Home » Easy Keto Sponge Cake With Rhubarb

Easy Keto Sponge Cake With Rhubarb

This keto sponge cake with rhubarb is moist and light enough to enjoy any time of the day – from brunch to afternoon tea, or as a dessert -and because it is both gluten-free and keto, so you could have a slice on all three occasions! Plus, rhubarb gives this keto sponge recipe a sweet and tart flavor that you can taste in each delicious bite!

keto sponge cake rhubarb

This keto sponge cake is another one of my family’s favorite desserts – besides this keto chocolate cake and this refreshing lime cake that also happens to be gluten and dairy-free. Oh, and I can’t forget these keto chocolate chip cookies made with hazelnut flour!

By itself, this basic keto sponge cake recipe is both flavorful and so easy to make, it will be one of those keto desserts that you will want to make time and time again – or you can add your favorite low-carb fresh or frozen fruit (as I have with rhubarb) to elevate it into something more divine!

What Is A Sponge Cake

A sponge cake is any cake that is leavened with whipped egg whites and sugar. Flour is then gently folded in to maintain the volume created by the air bubbles from the whipped egg whites. Butter and egg yolks are also often used to increase the moisture content of a sponge cake, like in this keto recipe. It is called “sponge cake” because the cake absorbs the flavors of anything added to it, like a sponge! This keto sponge cake is infused with the sweet and tart flavor of rhubarb throughout, however, it will absorb any flavor that you choose to add to it!

What Makes A Keto Sponge Cake Different?

keto sponge cake sliced on platter

To make a keto sponge cake, you need to make a few adjustments and substitutions for a few ingredients that are in a traditional sponge cake recipe. First, you’ll need to use keto flour like almond or coconut flour in place of wheat flour. Secondly, you will need to add a second leavening agent like baking powder to give the denser keto flour some extra lift when baking. And lastly, traditional granulated sugar needs to be replaced with a keto sweetener like granulated erythritol, monk fruit, or allulose.

Here are a few of my recommendations:

Coconut and other nut flours with a high-fat content tent to brown rapidly when baked. To avoid excess browning, cover the cake pan with aluminum foil halfway through the baking time – otherwise, a light dusting of powdered erythritol over the sponge cake will cover the darker areas!

Pro Tip

What You Need To Make A Keto Rhubarb Sponge Cake

keto sponge cake ingredients

Equipment

  • Mixing bowls – one for egg whites, one for the egg yolks mixture, and one for the dry ingredients
  • Electric or hand mixer – necessary to get stiff peaks in the egg whites and to cream the yolks properly with the sugar
  • Mixing spoon or spatula – needed to carefully fold the egg whites into the sponge batter
  • 9-inch springform cake pan – this pan allows for the height of the baked keto sponge cake
  • Parchment paper – to line the bottom of the cake pan and allow for easier removal

Wet Ingredients

  • Eggs, separated
  • Melted butter – must be cooled before adding to the mixture so that the eggs do not “scramble”
  • Full Fat Greek Yogurt – makes the sponge moist while adding fat
  • Unsweetened almond milk – has the most neutral flavor and the lowest carbohydrates of all milk choices
  • Vanilla extract or vanilla powder – either add extra flavor to the cake
  • Rhubarb or other low-carb fruit – sliced into .5 to 1-inch cubes (1-2.5 cm)
keto sponge cake frozen rhubarb
I used frozen rhubarb!

Dry Ingredients

  • Almond Flour – use blanched and lightly ground for a light sponge
  • Coconut flour – makes for a softer texture and holds moisture in
  • Baking powder – an extra leavening agent for the gluten-free/keto flour
  • Lemon zest – gives the cake a fresh flavor that balances the sweetness of the rhubarb
  • Granulated sugar substitute – to whip into the egg yolks

How To Make Keto Sponge Cake (Slideshows)

Step 1:

In a mixing bowl, beat the egg whites until stiff peaks form. Set aside.

keto sponge cake egg whites beaten

Step 2:

In another bowl, whisk the egg yolks with the granulated sweetener. Add in the vanilla, lemon zest, cooled melted butter, greek yogurt, and milk. Whisk until combined.

  • keto sponge cake egg yolks and sugar
  • keto sponge cake egg yolks beaten
  • keto sponge cake vanilla added
  • keto sponge cake vanilla beaten

Step 3:

Place a sifter over another mixing bowl and place the almond and coconut flour along with the baking powder into the sifter. Shake the sifter until the dry ingredients pass through. Discard any larger unsifted pieces.

  • keto sponge cake dry ingredients in sifter
  • keto sponge cake large bits in sifter
  • keto sponge cake dry ingredients sifted

Step 4:

Add the dry ingredients to the wet ingredients and whisk. Add the whisked egg whites and gently fold them into the cake batter.

  • keto sponge cake add dry ingredients to wet
  • keto sponge cake mixing batter
  • keto sponge cake egg whites added to batter
  • keto sponge cake folding in egg whites

Step 5:

Next, gently fold in the diced fruit, if desired. Spoon the batter into a cake pan lined with parchment paper. Bake 50-55 minutes or until a toothpick comes out clean from the middle of the cake. Allow it to cool before slicing.

  • keto sponge cake folding in rhubarb
  • keto sponge cake placing batter in pan
  • keto sponge cake ready for the oven

What To Serve With a Keto Sponge Cake

keto sponge cake garnish
  • Full-fat Greek yogurt
  • Whipped heavy cream
  • Fresh berries
  • Powdered erythritol
  • Fresh mint or thyme

What Other Keto-Friendly Fruits Can I Use In This Sponge Cake

This is one of those low-carb sponge cake recipes that can be enjoyed year-round and adapted to seasonality. And because the keto sponge cake recipe is so versatile, you can add just about any low-carb fruit! Here are some seasonal suggestions:

SeasonFruit (grams net carbs per cup)
Spring/SummerBlackberries (6g), Coconut: year-round (5g), Raspberries (5g), Rhubarb (4g), Strawberries (6g)
Autumn/WinterClementines (8g), Cranberries (8g)

Can I Use Frozen Fruit in a Keto Sponge Cake Recipe?

keto sponge cake fresh and frozen fruit

Yes, you can absolutely use frozen fruit in this recipe – in fact, I am an advocate for it! It helps to cut down on waste, plus because frozen fruit is packaged at its peak of freshness, it retains all of the vitamins and minerals while maintaining the best flavor! I used frozen rhubarb for my keto sponge cake that I had leftover and packaged from last summer.

How To Store The Sponge Cake

Refrigerated:

Because the keto sponge recipe contains fruit, it is best to store the cake in the refrigerator covered in plastic wrap or a storage container for up to a week. If making a plain sponge cake, you may store the cake at room temperature for up to 5 days. However, wrap it in plastic or seal it to keep it moist.

Freezer:

Wrap the cake in plastic or place it in an air-tight container and freeze for up to 4 months. To thaw, simply remove the cake from the freezer and place it on a room-temperature counter for a few hours.

The Recipe:

keto sponge cake thumbnail

Easy Keto Sponge Cake With Rhubarb

FamilyandGlamour
This keto sponge cake is delicious, light, and so easy to make! It is a basic recipe that will soak up any flavor you add to it, like this recipe with sweet and tangy rhubarb! Use your imagination and impress family and friends with seasonal fruit fillings and a dollop of fresh yogurt or cream on the side – no one will believe it's gluten-free and keto with only 4.7 net carbs per slice!
4.88 from 8 votes
Prep Time 10 mins
Cook Time 55 mins
Total Time 1 hr 5 mins
Course afternoon tea, Dessert
Cuisine American, British, International
Servings 12
Calories 234 kcal

Ingredients
  

Wet Ingredients

Dry Ingredients

Keto Fruit

  • 1½-2 cups rhubarb, or keto fruit of choice, cut into ½-1-inch cubes (244 grams of rhubarb)

Instructions
 

Prepare For Baking

  • Preheat the oven to 350°F/180°C. Line the bottom of a springform pan with parchment paper.

Prepare The Wet Ingredients

  • Separate the egg whites into a mixing bowl. Set the yolks aside in a separate bowl. With an electric mixer, whisk the egg whites until stiff peaks form. Set aside.
  • Add the granulated sweetener to the bowl with the egg yolks. With the electric mixer, whisk the egg yolks and the sugar until creamy and the mixture is light in color. Add the vanilla, melted and cooled butter, milk, and lemon zest (or extract). Whisk the ingredients until combined.

Prepare The Dry Ingredients

  • Place a sifter over another empty mixing bowl. Place the almond and coconut flour along with the baking powder into the sifter. Shake the sifter back and forth until all of the flour has fallen through into the bowl and only larger pieces remain in the sifter. Discard the larger pieces.

Combine To Form The Sponge Batter

  • Add the dry flour mixture into the egg yolk mixture. Whisk them together until they are well combined.
  • With a spatula or spoon, GENTLY fold the whipped egg whites into the cake batter until combined.

Optional Keto Fruit:

  • Gently fold in the rhubarb or other keto fruit of choice.

Bake

  • Spoon the batter into the prepared cake pan, making sure the batter is distributed evenly and the surface is as smooth as possible. Bake 50-55 minutes or until a toothpick is inserted into the center of the cake and comes out clean and dry (cover the cake halfway through baking time to avoid excess browning). Allow the cake to cool completely before removing the springform. Garnish with powdered sweetener, fruit, whipped cream, or yogurt.

Video

Notes

  • The nutritional values listed in the recipe card include rhubarb.  You can check the nutritional values for a specific fruit on a site like: https://www.nutritionvalue.org/
 
Here are the nutritional values for a plain keto sponge cake:
Calories 229  Total Fat 20g  Saturated Fat 7.1g  Cholesterol 99mg  Sodium 206mg Total Carbohydrate 6.8g    Dietary Fiber 2.6g     Sugar 3.9g   Protein 7.9g  Calcium 132mg Iron 0.6mg Potassium 107mg 

Nutrition

Sodium: 207mgCalcium: 149mgSugar: 4.2gFiber: 3gPotassium: 165mgCholesterol: 99mgCalories: 234kcalSaturated Fat: 7.2gFat: 20gProtein: 21gCarbohydrates: 7.7gIron: 0.7mg
Keyword afternoon tea, almond flour, coconut flour, gluten-free, keto cake, keto dessert, rhubarb, sponge cake
Tried this recipe?Let us know how it was!

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