Orange & Olive Oil Upside Down Cake

Olive oil in cakes… who would’ve thought that this would be even better than butter? Although having a very similar ingredient ratio to a pound (bundt) cake, swapping butter for olive oil in this keto orange cake gave it an otherworldly deliciousness.

The crumb still looks dense and well woven as you’d expect from a pound cake, but when you bite into it, it feels completely different. It’s just so tender. Sooo moist. I ate it in disbelief. It was impossibly amazing.

Using an hemisphere cake pan for this keto orange and olive oil cake gave it a unique, planetary look that I’m just in love with! This is definitely a summer cake, which will grace your table like a golden, cheery ray of sunshine. See how happy this cake looks!

A beautiful smiling fluffy hemisphere shaped cake, covered in golden orange slices.

Have you ever tried baking an upside down cake? You don’t need an hemisphere pan to do it, although they look just amazing in any sort of flat bottomed pan as well. They are really very easy to make!

Decorating this keto upside down cake is just one extra fun step in the pan preparation, and when you turn the cake BAM! The cake is done. It’s not only upside down, it’s from finish to start. In a sense. Because you decorate the cake before the cake is even baked. It’s almost like time travel.

No butter, no sugar, no milk, no gluten… The impossible cake?

Why substitute butter for olive oil in cakes?

Baking with liquid oils such as olive or avocado oil will make the finished result seem to last longer fresh and moist than when using butter or coconut oil. Saturated fats, which are solid at room temperature, make for rich baked goods but, after cooling down, the fats re-solidify.

This explains why butter cakes – such as pound cakes – can feel drier and heavier. Cakes baked with liquid oils are lighter and have an almost juicy characteristic, in a sense that you can feel the moistness flood through your mouth. Inundating you with pleasure.

A large slice of olive oil and orange inverted low-carb cake.

Tips for baking cakes with olive oil

  • Use a good quality extra virgin olive oil. You’ll be using a generous amount, and the flavor and texture of your cake will depend on it.
  • When using olive oil instead of butter, generally you should use about 25% less oil than the butter equivalent. For example, use 3/4 cup of oil instead of 1 cup of butter.
  • Reduce, or even remove all of the other liquids from the recipe. Think milk, buttercream, water and liquid flavors that are added in a larger amount, like tea, coffee and fruit juices. The olive oil already behaves like a liquid, add more liquids and you risk ending with a runny batter. For this keto recipe, instead of using orange juice, I used orange extract and zest. This way, we get all the orange flavor without the extra sugar and carbs and keep the batter from getting too wet.
  • Oil can’t be aerated by creaming like butter, where often you can just beat it together with sugar for leavening and call it a day. When making an oil based cake you can’t escape adding baking powder. And, as this recipe has an acidic component (yogurt), I decided to take advantage of it by including a little bit of baking soda as well to improve the rise. Cakes baked with heavier keto or gluten-free flours, such as almond flour or coconut flour, can always use some leavening help for extra fluffiness.
A sliced olive oil and orange sugar-free cake, showing its tender, fluffy cake crumb.

How to make the upside down orange cake topping, step by step

  • Butter the pan with a very thick layer of room temperature butter (or ghee). Dust the buttered pan with an even layer of sweetener. Use a fine metal mesh or sieve to sprinkle the sweetener uniformly.
  • Wash the orange (or oranges – see below). Using a grater, remove the peel of the orange gently. You just need the orange colored part, and 1 orange should make around one tablespoon of zest.
Step by step pictures of how to prepare the keto orange and olive oil cake upside down topping.
Butter pan, sprinkle erythritol, zest and slice oranges, blot slices, arrange slices, blot juice again before pouring batter
  • Using a very sharp knife, slice the orange in thin slices, as uniformly as possible. Try not to squeeze the orange while holding it, to keep the shape round.
  • Blot dry the orange slices, by pressing one by one in between folded sheets of paper towel. Make them as dry as you can.
  • Carefully arrange the dried orange slices on top of the buttered and sugared pan. If you want no gaps of cake peeking through in between the slices, you’ll have to overlap them, by covering about 1/3 of a slice with a new one. This is because the slices will shrink down quite a bit while in the oven. My cake came out with a lot of peekaboo even though the slices were really crammed in together. To get a full coverage effect, you’ll need 2 oranges instead of one. Either way you arrange, your cake is gonna look beautiful!
A big slice of keto olive oil and orange upside down cake.

After you are satisfied with your slices arrangement, evenly cover the orange slices with some more powdered erythritol. Set it aside, and start preparing the upside down keto cake batter.

Before pouring the batter over the slices, have a look at them. Although you squeezed out the most of the juice, the sweetener might have made the orange slices “sweat” out a bit more liquid. If that’s the case, just carefully press down on them with a paper towel to absorb the remaining juice.

How to make the keto olive oil and orange cake

In a medium bowl, whisk together all the dry ingredients, except for salt. You can also skip this step, and just sieve them all in on top of the wet mixture later on.

In a larger bowl, add the olive oil, keto sweetener and salt. Whisk them together for 2-3 minutes. You can either use a standing mixer or an electric hand mixer with a whisk attachment, or just a regular balloon whisk if you’re feeling particularly energetic.

A lovely half hemisphere shaped gluten-free cake covered in golden orange slices.

Then add the eggs, one by one, whisking very well after each addition. Continue mixing for 3 more minutes, until the mixture is pale and foamy.

Add the yogurt, orange extract and orange peel, and mix it for a minute more.

Drop the dry mix onto the wet mix, or sieve it all in, and combine it all very well using a spatula. The mixture should be well homogenized. The batter is thick and very shiny!

Pour the batter gently over the orange arrangement, and massage the batter down with the spatula to remove air bubbles. Careful not to dislodge the orange slices below.

After baking, place the keto oil cake on a cooling rack until it’s comfortable enough for you to touch the pan, at least 20 minutes. The cake should be turned upside down while it’s still warm, to prevent the orange slices from sticking to the bottom as they cool.

Update: You can substitute oat fiber for pea protein

My husband asked what I wanted for my birthday, and I said:

A cake! But a cake that you make, with love, not a bought cake. Anyone can buy a cake. Only people who love make a cake.

He agreed to demonstrate his love for me on my special day by baking me a keto cake 🥰 And when he asked which cake, I promptly directed him to this blog post 😂 It’s one of my favorites, very festive looking without much fuss, and reasonably easy. So I’m nice!

Thing is, while he was mixing the ingredients, he asked me where the oat fiber was. Oops… It had run out a while ago and I didn’t replenish. As I’d have to ship it in, we had to find a replacement. I started looking through the pantry, wondering what could be a good oat fiber substitution for this upside down keto cake. Solution: Pea protein powder.

Yes, the oil cake came out wonderfully! Pea protein powder has a very similar texture to oat fiber, you can’t really tell much difference in taste, and if you are looking to squeeze protein into everything to hit your macros – there’s an idea for you!

Share with your friends,
they might cook for you!

Yield: 10 slices

Olive Oil & Orange Upside Down Cake

A big slice of keto olive oil and orange upside down cake.

An impossibly moist and fluffy pound cake, thanks to the substitution of butter for olive oil. Gluten-free, sugar-free & keto!

For US Cups conversion, check Notes.

Prep Time: 25 minutes
Cook Time: 1 hour
Total Time: 1 hour 25 minutes


For the upside down topping

  • 1 (or 2, see details in post) big, nicely shaped orange, washed, and cut into thin slices
  • 1 tablespoon of powdered erythritol
  • 1 tablespoon of room temperature butter or ghee

For the cake

  • 155 grams almond flour
  • 50 grams oat fiber (or pea protein)
  • 130 grams keto sweetener
  • 3 eggs
  • 110 grams olive oil, light tasting
  • 80 grams natural yogurt
  • 1/4 teaspoon salt
  • 1 teaspoon orange extract
  • 2 teaspoons baking powder
  • 1/8 teaspoon baking soda
  • 1 tablespoon psyllium husk
  • 1 tablespoon orange zest


For the upside down topping

1. Heavily butter the whole pan, with room temperature butter (or ghee), and sprinkle it with an even layer of sweetener

2. Zest the orange carefully to keep it from deforming it. You just need the orange colored part.

3. With a sharp knife, slice the orange into thin and uniform slices.

4. Using paper towels, dry the orange slices by pressing tthem in between folded sheets of paper towel.

5. Arrange the dried orange slices inside the pan, then evenly cover them with a layer of sprinkled erythritol.

For the cake

1. Whisk together all the dry ingredients (except for salt): almond flour, oat fiber, baking powder, baking soda and psyllium husk. Alternatively, you can later sieve them directly over the wet mixture.

2. In a separate, larger bowl, whisk together the olive oil, erythritol and salt.

3. Add the eggs, one by one, whisking after each addition. Continue mixing for 3 more minutes, until the batter is pale and foamy.

4. Add the yogurt, orange extract and orange peel, and whisk it for a minute more.

5. Drop (or sieve in) the dry mix onto the wet mix, and combine it all very well with a spatula until homogenized. The batter will look very shiny and thick.

6. Take the prepared pan, and if necessary dry up the orange slices arrangement with a paper towel before pouring in the batter.

7. Bake on the middle rack position in the preheated oven at 175 °C (347 °F) for the first 25 minutes. Then loosely cover the top with an aluminum foil and turn the oven temperature down to 160 °C (320 °F), and bake for another 35 minutes until you can smell the cake ready.

8. Remove the foil to test with a toothpick, it should come out mostly clean, a couple of crumbs are okay.


US Cups approximate conversion: Use 1 1/2 cup almond flour, 1/2 cup oat fiber (or pea protein), 3/4 cup erythritol stevia, 1 cup olive oil and 1/3 cup yogurt. Other ingredients as indicated.

I used an 8" hemisphere pan. You can use any 8" pan, or a tall 7" pan, or a medium loaf pan.

Using room temperature or slightly warm butter or ghee (instead of just out of the fridge) makes it easier to spread a thicker buttering layer. You'll need a thick layer under the orange slices.

The cake must be turned while it’s still warm, to prevent the orange slices from sticking to the bottom it cools.

If gluten-free, make sure the oat fiber is gluten-free certified. Although oats are naturally gluten-free, there may be cross-contamination from wheat crops or during processing, as some brands state in their packages.

I mix stevia and erythritol to make it 100% as sweet as sugar. This way, I can use less erythritol, avoiding the cooling taste that shows up when it's used in excess, while also masking the bitter aftertaste of stevia and bulking it up. If you want to make your own 1:1 keto sugar, click here to learn how.

Nutrition information shows recipe made with oat fiber. Recalculate for pea protein substitution.

Nutrition Information:

Yield: 10 Serving Size: 1
Amount Per Serving: Calories: 254Total Fat: 20.9gSaturated Fat: 1.2gTrans Fat: 0gCholesterol: 55.8mgSodium: 28.5mgCarbohydrates: 10.9gNet Carbohydrates: 3gFiber: 7.9gSugar: 1.9gProtein: 5.6g

Nutritional information is provided as a guideline only. Different brands of ingredients may have different nutrition facts. If you are doing a very strict form of keto, such as for medical purposes, please do remake the calculations using the nutrition facts from the labels of the ingredients you selected. Net carbs calculated exclude carbs from insoluble fiber and the sugar alcohol erythritol.

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12 thoughts on “Orange & Olive Oil Upside Down Cake”

    1. Hi Zeinab, thanks for your question. You could use 1/2 teaspoon of xanthan gum, it will have a similar effect. You can still bake the cake without if you don’t want it, but the texture of the cake, as in being moist and fluffy, won’t be as good. I do recommend getting some psyllium if you bake keto or gluten-free often 🙂

  1. Jacquelyn Hastert

    I have this keto olive oil cake saved and will be making it in the very near future. It sounds easy and delicious!

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