Fluffy Protein Coffee Cake with Cinnamon Streusel

This protein coffee cake has a soft, buttery crumb, a sweet cinnamon ribbon right through the middle, and a crisp streusel top. It bakes up in about 30 minutes and gives you over 10 grams of protein per slice, so it works just as well for a lazy weekend brunch as it does for a quick weekday breakfast.

Why I Keep Coming Back to This Protein Coffee Cake

The Greek yogurt and applesauce keep the crumb noticeably moist for days, so you never bite into the dry, chalky texture some protein bakes end up with. That ribbon of cinnamon sugar and the buttery streusel deliver the classic coffee shop coffee cake you actually want, just with a lot less sugar and a solid protein boost.

Ingredients

• 1 cup oat flour: spoon and level; use certified gluten-free if needed.
• 1/2 cup vanilla protein powder: whey or plant-based, pick one you like the taste of.
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon fine sea salt
• 1 teaspoon ground cinnamon
• 1/2 cup plain Greek yogurt: full-fat gives the moistest crumb.
• 1/4 cup unsweetened applesauce
• 1/4 cup melted unsalted butter: or melted coconut oil.
• 1/4 cup maple syrup: honey works too.
• 1 large egg
• 1 teaspoon vanilla extract
• 2 tablespoons coconut sugar: or brown sugar (for the swirl)
• 1 teaspoon ground cinnamon: for the swirl
• 1/4 cup oat flour: for the streusel
• 2 tablespoons melted butter: for the streusel
• 2 tablespoons coconut sugar: or brown sugar (for the streusel)
• 1/2 teaspoon ground cinnamon: for the streusel

Variations

• Make it dairy-free: use coconut yogurt, melted coconut oil, and a plant-based protein powder.
• Swap the protein flavor: unflavored or chocolate powder changes the profile; vanilla keeps it classic.
• Add crunch: fold 1/4 cup chopped pecans or walnuts into the streusel for extra protein and texture.
• Change the sweetener: honey, agave, or sugar-free maple syrup all work, adjust to your taste.

If you like this, try my Blueberry Protein Muffins recipe.

How To Make Protein Coffee Cake

Step 1: Whisk the Dry Ingredients

Preheat the oven to 350°F (175°C) and line an 8-inch square baking pan with parchment paper. In a large bowl, whisk together 1 cup oat flour, the 1/2 cup protein powder, baking powder, baking soda, salt, and 1 teaspoon cinnamon until no lumps remain.

The mixture will look pale and uniform. A couple of minutes of whisking distributes everything evenly so the cake rises well.

Step 2: Mix the Wet Ingredients

In a separate bowl, combine the 1/2 cup Greek yogurt, 1/4 cup applesauce, 1/4 cup melted butter, 1/4 cup maple syrup, the egg, and vanilla extract. Whisk until smooth and fully combined, about 30 seconds.

The wet mixture should be creamy and pourable, with no streaks of egg or yogurt. If the butter is still hot, let it cool for a minute so it doesn’t scramble the egg.

Step 3: Stir the Batter and Prep the Swirl

Pour the wet ingredients into the dry ingredients and stir with a spatula just until you no longer see dry flour. A few small lumps are fine; overmixing will make the cake tough.

In a small bowl, stir together the 2 tablespoons coconut sugar and 1 teaspoon cinnamon for the swirl.

Step 4: Layer the Batter and Cinnamon Swirl

Spread half of the batter into the prepared pan and smooth it into an even layer. Sprinkle the cinnamon sugar mixture over the top, covering the surface as evenly as you can. Dollop the remaining batter on top and gently spread it to cover the swirl, using a light touch so the cinnamon layer stays distinct.

The batter will be thick but spreadable. A small offset spatula or the back of a spoon dipped in water helps if it sticks.

Step 5: Make the Streusel and Bake

In the same small bowl, mix the 1/4 cup oat flour, 2 tablespoons melted butter, 2 tablespoons coconut sugar, and 1/2 teaspoon cinnamon with a fork until it looks like moist, sandy clumps. Scatter the streusel evenly over the top of the batter.

Bake for 28 to 32 minutes, until the top is golden and a toothpick inserted in the center comes out with just a few moist crumbs. The streusel will feel set and lightly crunchy.

Step 6: Cool, Slice, and Serve

Let the cake cool in the pan for 10 minutes, then use the parchment overhang to lift it out onto a wire rack. Slice into 8 squares and serve warm or at room temperature, with the cinnamon swirl peeking through each piece.

A Few Notes Before You Start

• Measure the oat flour correctly: spoon it into the cup and level; scooping compacts it and can dry out the cake.
• Don’t overmix the batter: stir just until no dry patches remain to keep the crumb fluffy, not dense.
• Check early if your oven runs hot: protein bakes dry out fast, so start testing at 25 minutes.
• Protein powder matters: if yours is unflavored, add an extra 1/2 teaspoon vanilla and a pinch more sweetener.

Bake times by pan:

Storing Leftover Coffee Cake

• Refrigerate: store slices in an airtight container for up to 4 days.
• Reheating: warm individual slices in the microwave for 20–30 seconds, or in a 300°F oven for 5 minutes to re-crisp the streusel.
• Serve cold: it’s just as good straight from the fridge.

What to Serve with This Protein Coffee Cake

A strong black coffee cuts through the sweetness and pulls out the cinnamon notes. For an even bigger protein hit, spoon some vanilla Greek yogurt over a warm slice.

Frequently Asked Questions

Can I use plant-based protein powder?

Yes. The batter may be a little thicker; stir in 1 tablespoon of milk if it seems too stiff.

Is this recipe gluten-free?

It can be. Use certified gluten-free oat flour and a gluten-free protein powder, and you are set.

Can I make it without eggs?

Yes. Use a flax egg (1 tablespoon ground flax mixed with 2.5 tablespoons water) and let the batter sit for 5 minutes before baking. The cake will be slightly denser.

What if I don’t have applesauce?

Substitute an equal amount of mashed ripe banana. The cake will pick up a faint banana flavor, but it stays moist.

Protein Coffee Cake Recipe

Print Recipe Pin Recipe

Prep Time 10 minutes mins

Cook Time 30 minutes mins

Total Time 40 minutes mins

Servings: 8 servings

Calories: 220

Ingredients Method Notes

Ingredients

  

• 1 cup oat flour
• 1/2 cup vanilla protein powder
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon fine sea salt
• 1 teaspoon ground cinnamon
• 1/2 cup plain Greek yogurt
• 1/4 cup unsweetened applesauce
• 1/4 cup melted unsalted butter
• 1/4 cup maple syrup
• 1 large egg
• 1 teaspoon vanilla extract
• 2 tablespoons coconut sugar
• 1 teaspoon ground cinnamon (for swirl)
• 1/4 cup oat flour (for streusel)
• 2 tablespoons melted butter (for streusel)
• 2 tablespoons coconut sugar (for streusel)
• 1/2 teaspoon ground cinnamon (for streusel)

Method

 

1. Preheat oven to 350°F (175°C) and line an 8-inch square baking pan with parchment. Whisk 1 cup oat flour, protein powder, baking powder, baking soda, salt, and 1 teaspoon cinnamon.
2. In another bowl, whisk the yogurt, applesauce, 1/4 cup melted butter, maple syrup, egg, and vanilla until smooth.
3. Stir the wet ingredients into the dry just until combined; a few lumps are fine.
4. Combine 2 tablespoons coconut sugar and 1 teaspoon cinnamon for the swirl.
5. Spread half the batter into the pan, sprinkle all the cinnamon sugar over it, then dollop and gently spread the remaining batter on top.
6. In a small bowl, use a fork to mix the 1/4 cup oat flour, 2 tablespoons melted butter, 2 tablespoons coconut sugar, and 1/2 teaspoon cinnamon until crumbly. Scatter over the batter.
7. Bake 28 to 32 minutes, until golden and a toothpick comes out with a few moist crumbs.
8. Cool in the pan for 10 minutes, lift out, slice, and serve.

Notes

The cake stays moist for days; store in the fridge up to 4 days. For the best flavor, use a protein powder you enjoy drinking because its taste comes through.