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!

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?

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

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)

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.

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.

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.

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.

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.

What To Serve With a Keto Sponge Cake

• 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:

Season	Fruit (grams net carbs per cup)
Spring/Summer	Blackberries (6g), Coconut: year-round (5g), Raspberries (5g), Rhubarb (4g), Strawberries (6g)
Autumn/Winter	Clementines (8g), Cranberries (8g)

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

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:

Have you ever tried a keto sponge cake with rhubarb?

Will you be trying this recipe? Comment below!