Preheat oven to 350 degrees.
Spray glass 8x8 inch pan with coconut oil spray.
In a large bowl, mash 2 overripe bananas (1 cup apple sauce can be used as a substitute)
Add cocoa powder, protein powder, nut butter (warm the nut butter in the microwave to make it workable), and vanilla extract to the bowl.
Mix all ingredients together. The batter should be thick but workable. You may need to add more banana or applesauce.
Spread evenly in your 8x8 inch pan and cook for about 20 minutes.