01 - Preheat oven to 350°F. Grease a standard 12-cup muffin tin or line each cavity with paper liners.
02 - In a large mixing bowl, combine the oats, protein powder, cinnamon, baking powder, and salt until evenly distributed.
03 - In a separate bowl, whisk the applesauce, egg, milk, maple syrup or honey, vanilla extract, and melted coconut oil or unsalted butter until the mixture is smooth.
04 - Pour the wet mixture into the dry ingredients and stir just until combined for a uniform batter.
05 - Gently fold in the finely diced apple to evenly distribute throughout the batter.
06 - Divide the oatmeal mixture evenly among the 12 muffin cups, filling each about three-quarters full.
07 - Place muffin tin in the oven and bake for 22 to 25 minutes, until tops are set and lightly golden.
08 - Let oatmeal cups cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely before serving or storing.