
Preheat an oven to 350F and place 6 silicone muffin molds on a baking sheet. (You can use a muffin tin with nonstick cooking spray or parchment baking cups as well.)
Whisk or mix the eggs, butter, apple sauce, vanilla, and brown sugar together until smooth. (I used a stand mixer on medium speed for 20-30 seconds.)
Mix the protein powder, flour, baking powder, and 1/2 tsp ground cinnamon together in a separate bowl. Fold the dry ingredients into the egg mixture.
Transfer the muffin batter to the muffin molds and sprinkle with the granulated sugar and remaining ground cinnamon.
Bake for 18-20 minutes or until a toothpick comes out clean. Enjoy!