Preheat the oven to 350 degrees Fahrenheit and generously spray two 6" cake pans with cooking spray.

In a large mixing bowl, whisk together the applesauce, egg whites, peanut butter, sucanat, erythritol, almond milk, and stevia extract.

In a medium-sized mixing bowl, whisk together the oat flour, peanut flour, and baking powder.

Sift the dry ingredients over the wet and stir together. Whisk the batter vigorously for 10-20 seconds, or until all of the clumps are gone.

Pour batter evenly into the prepared pans and bake for ~52 minutes, or until surface is golden brown and springs back when tapped. Remove cakes from oven and let cool in the pans for 5 minutes, then turn them out onto a wire cooling rack.

In a stand mixer bowl with whisk attachment, add the protein powder and cocoa powder. Whisk on low.

Increase mixer speed to medium and slowly drizzle in the almond milk. Add the stevia. Whisk until creamy and fluffy. Frost the cake and refrigerate for ~30 minutes to firm the frosting. Slice and serve!