This moist and fluffy protein cake is soft, tender, and actually tastes like cake. It’s made with oat flour, whey protein, and a small blend of olive oil and butter for the perfect crumb. Lightly sweetened with maple syrup and finished with a rich two-ingredient fudge frosting, it’s a better-for-you dessert that still feels indulgent.
Healthier desserts can be tricky when you want real cake texture and good nutrition. This protein cake took a few test bakes to find that balance, and a small blend of olive oil and butter made all the difference. The result is a moist, fluffy cake that feels like a real dessert, not a compromise.
If you’ve tried my protein cupcakes, this cake has a very similar soft, fluffy texture — just in cake form.
Here’s why this protein cake is one you’ll want to make again and again.
Why you will love this protein cake
- It’s moist and fluffy, not dense or dry
- Made with oat flour for a soft, tender crumb and a more nutritious alternative to all-purpose flour.
- Lightly sweetened with maple syrup
- The two-ingredient fudge frosting comes together in less than 5 minutes.
- Works as a healthier dessert or a satisfying post-workout protein treat.
- Made with simple, everyday ingredients.
Key Ingredients + Substitutions
- Oat Flour- Oat flour gives this protein cake a soft, tender crumb and adds more whole-grain nutrition than all-purpose flour. If you’re making your own, use finely blended oats for the best texture. I share more tips and troubleshooting in my oat flour guide if you’re new to baking with it.
- Vanilla Whey Protein Powder- I used Levels Vanilla Bean Whey Protein. Feel free to use any vanilla whey protein you enjoy. I can't guarantee the same results using a plant-based protein powder because it tends to be more absorbent than whey. If you decide to use a plant-based protein, add a splash (about 2 tablespoons) of milk of your choice to the batter.
- Cornstarch- Cornstarch helps keep the protein cake light and tender, especially when baking with protein powder. You can substitute arrowroot starch 1:1 or use tapioca starch (use 1½ tablespoons of tapioca for every 1 tablespoon of cornstarch, so 6 tablespoons total).
- Olive Oil + Butter- A small blend of olive oil and butter keeps the cake moist and flavorful without making it heavy. You can use all olive oil if needed, but the butter adds richness and improves the crumb.
- Maple Syrup- Maple syrup lightly sweetens the cake and keeps it moist. Liquid sweeteners work best here; swapping to a dry sweetener would change the texture.
- 2-Ingredient Fudge Frosting- The frosting is simply chocolate chips and peanut butter. It spreads easily while warm and sets into a thicker, fudge-like layer as it sits.
Step-by-Step Photos (So You Know You’re On Track)
Use these step-by-step photos as a quick visual guide while baking.
Batter in the bowl
Thick but smooth and pourable. Slightly thicker than pancake batter.
Batter in the pan
Thin enough to spread on its own — no smoothing needed.
Right out of the oven
Lightly golden and set in the center.
Frosting
Smooth, glossy, and easy to spread while warm.
Protein Cake FAQs
For this recipe, I used vanilla whey protein powder, which gives the best texture and flavor. Plant-based protein powders tend to be more absorbent and can make the batter thicker. If you use a plant-based protein, add 2 extra tablespoons of milk to keep the cake soft and fluffy.
Letting the batter rest for a few minutes allows the oat flour to hydrate, which helps the cake bake up softer and more evenly.
Yes. Once fully cooled, slice the protein cake and wrap each piece tightly in plastic wrap. Store the wrapped slices in a freezer-safe bag or container for up to 2 months. Thaw overnight in the refrigerator or at room temperature before serving.
More Protein Desserts
Happy baking! If you make this protein cake, I’d love for you to leave a rating below — it really helps and means so much.
— Crystal
📖 Recipe
Protein Cake (Moist & Fluffy!) with 2-Ingredient Fudge Frosting
Ingredients
For the cake
- 1 and ½ cups oat flour*
- ½ cup vanilla whey protein powder*
- ¼ cup cornstarch
- 1 tablespoon baking powder
- ½ teaspoon salt
- ⅔ cup maple syrup or liquid sweetener of choice
- 2 large eggs
- 3 tablespoons olive oil or neutral oil
- 2 tablespoons butter melted
- 3 tablespoons milk of choice
- 2 teaspoons vanilla extract
For the frosting
- ½ cup chocolate chips of choice
- 2 tablespoons peanut butter* see notes
Instructions
For the Cake
- Preheat the oven to 335ºF. Lightly spray an 9-inch round cake pan with non-stick spray, line the bottom with a parchment round, then spray the parchment. This ensures your cake doesn't stick. (You can also just spray the pan if you prefer.)
- In a large bowl, whisk together the oat flour, protein powder, cornstarch, baking powder, and salt.
- In a separate bowl, whisk together the maple syrup, eggs, olive oil, melted butter, milk, and vanilla until smooth.
- Pour the wet ingredients into the dry ingredients and stir until just combined. Let the batter rest for 4–5 minutes to allow the oat flour to hydrate, then give it a quick stir.
- Pour the batter into the prepared cake pan. Bake for 22–25 minutes or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Let the cake cool for 10 minutes in the pan before transferring it to a wire rack to cool completely.
For the frosting
- When the cake is cool, prepare the fudge frosting.
- Melt the chocolate chips and peanut butter together in the microwave in 20-second intervals, stirring until smooth.
- Spread the frosting over the cooled cake (the sides can be left unfrosted). It’s delicious right away, or let it sit for a few hours to set into a fudge-like layer.
- Slice, serve, and enjoy! Please leave a rating if you try this recipe.
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