This is a single-pan protein cake made from blended oats, egg whites, and vanilla protein powder, with a cinnamon layer swirled through the middle. It takes 17 minutes start to finish, and the part that matters most is blending the batter until it’s fully smooth — leftover oat texture is what makes these turn out gummy instead of cake-like.
Quick facts
| Prep time | 5 minutes |
|---|---|
| Cook time | 12 minutes |
| Total time | 17 minutes |
| Servings | 2 |
| Difficulty | Easy |
Why this version works
Blending the oats fully into the batter, instead of leaving them coarse, is what gives this a cake-like crumb instead of a gummy one. Layering half the batter, then cinnamon, then the rest, and only lightly swirling with a knife keeps the cinnamon as a defined ripple instead of blending it into the whole cake. A small 4.5-inch pan matters too — a wider pan spreads the batter too thin and it cooks dry before the center sets.
Ingredients
- ½ cup oats
- ¼ cup (4 tbsp) liquid egg whites (about 2 large egg whites)
- ⅔ cup water
- 2 scoops vanilla protein powder (about 2 oz)
- 1 tsp stevia
- 1 tsp baking powder
- 1 tbsp cinnamon
Substitutions
- Sweetener: swap stevia for monk fruit sweetener or regular sugar, same amount.
- Protein powder: chocolate protein powder works for a mocha-style version instead of vanilla.
- Oats: quick oats or rolled oats both blend smooth — no need for one over the other.
- Gluten-free: use certified gluten-free oats to keep this recipe gluten-free.
How to make cinnamon swirl protein cake
- Preheat. Set your oven to 390°F (200°C) and let it fully heat before you start mixing — a cold oven throws off the bake time.
- Blend the batter. Combine oats, egg whites, water, protein powder, stevia, and baking powder in a blender. Blend until completely smooth, with no visible oat pieces left — this is what keeps the texture cake-like instead of gummy.
- Layer the base. Pour half the batter into a small 4.5-inch nonstick pan. Sprinkle the cinnamon evenly over this layer.
- Top and swirl. Pour the remaining batter over the cinnamon. Drag a knife through the batter a few times to create a marbled swirl — a few strokes is enough, more than that blends the cinnamon in completely and you lose the ripple.
- Bake. Bake 12 minutes, then check with a toothpick inserted in the center — it should come out clean or with a few moist crumbs, not wet batter. Add 1–2 minutes if it’s not there yet.
- Rest and slice. Let the cake cool in the pan for at least 5 minutes before removing and slicing — cutting into it too early makes it fall apart.
Pro tips
- Use a small nonstick pan so the cake releases cleanly without tearing.
- If the cake doesn’t rise well, try a different brand of protein powder — some contain additives that flatten the rise.
- A few knife strokes are enough for the swirl; more than that mixes the cinnamon in completely.
- A light spray of oil in the pan helps release even with a nonstick surface.
Common mistakes
- Gummy texture — almost always from underblending, leaving oat pieces in the batter instead of a smooth mix.
- Cake doesn’t rise — check your baking powder is fresh, or try a different protein powder brand.
- Swirl disappears entirely — too many knife strokes blend the cinnamon layer into the batter instead of marbling it.
- Cake falls apart when sliced — it needs the full 5-minute rest in the pan before you cut into it.
Storage and reheating
Store in an airtight container in the fridge for 3–4 days. Reheat a slice in the microwave for about 30 seconds to bring back the fresh-baked texture.
Nutrition (per serving, approximate)
| Calories | ~180 |
|---|---|
| Protein | ~24g |
| Carbs | ~13g |
| Fat | ~3g |
Exact numbers vary by protein powder brand — check the label on yours for the most accurate count.
Quick answers
Can I use a different protein powder flavor?
Yes, chocolate protein powder works well and gives it a mocha-style flavor.
Is this gluten-free?
Yes, as long as you use certified gluten-free oats.
Can I bake this in a larger pan?
Not well — this recipe is sized for a 4.5-inch pan. A larger pan spreads the batter thin and it dries out before the center sets.
Do I need to grease the pan?
Yes, even with a nonstick pan, a light spray of oil helps it release cleanly.
Why is 2 egg whites listed as 4 tablespoons instead of 6?
2 large egg whites measure closer to 4 tablespoons (about 2 oz). If your batter feels too thick, don’t add extra egg white to make up a 6-tablespoon amount — add a splash of water instead.
Can I double this recipe?
Yes, but bake it in two separate 4.5-inch pans rather than one larger pan, or the center won’t cook through in the same time. For another quick, protein-forward breakfast, the protein waffles scale up easily too.
Serving suggestions
- Top with a dollop of Greek yogurt for extra creaminess.
- Add fresh blueberries or raspberries for color and a bit of tartness.
- Drizzle a small amount of almond butter over the top.
- Serve with a hot cup of coffee or tea.
A few more high-protein treats to try
If you liked the warm cinnamon flavor here, the cinnamon apple breakfast quinoa leans on the same spice in a completely different format. For a make-ahead protein dessert, the protein cheesecake jars are worth trying next. Want something you can batch and keep on hand? The cottage cheese protein cookies store well for a few days. And for another single-serving breakfast bake, the cottage cheese breakfast rounds come together just as fast.
The first time I made this, I only pulsed the blender a few times and the finished cake had a slightly gritty, oat-heavy bite instead of a smooth crumb. Now I blend it until it’s genuinely smooth, almost like a thin pancake batter, and the texture comes out right every time.
