Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or grease it lightly.
In a large mixing bowl, combine the rolled oats, protein powder, almond flour, baking powder, ground cinnamon, and salt. Whisk together until well combined.
In another bowl, mix together the applesauce, eggs, honey (or maple syrup), vanilla extract, and almond milk. Stir until smooth.
Pour the wet ingredients into the dry ingredients and mix until just combined. Be careful not to overmix. If desired, fold in the chopped walnuts or pecans at this stage.
In a small bowl, mix the brown sugar and ground cinnamon for the topping.
Spoon the muffin batter into the prepared muffin tin, filling each cup about 2/3 full. Sprinkle a pinch of the cinnamon sugar mixture on top of each muffin.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted in the center comes out clean.
Allow the muffins to cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
Serve warm with a drizzle of honey or frosting made with Greek yogurt for added creaminess.