In a small bowl, whisk together 1/2 c. sugar and 1 tbsp. cinnamon. Set aside for swirling.
In a large bowl, whisk together oat flour, protein powder, cinnamon, baking powder, and 1/2 c. sugar.
In a medium bowl, whisk together egg whites, almond milk, and applesauce.
Add the wet ingredients to the oat flour mixture, stirring until just combined.
Fold in the blueberries.
Spray a 9-inch square pan with cooking spray.
Pour 1/3 of the batter into the pan, and sprinkle with 1/3 of the cinnamon-sugar mixture. Repeat with remaining batter, finishing with cinnamon-sugar on top.
Using a knife or toothpick, swirl the batter lightly for a marbled effect.
Bake at 350 degrees for 30-35 minutes, or until edges are golden brown, and a toothpick inserted near the center comes out clean. Enjoy!