Preheat your oven to 175°C (350°F). Line a muffin tin with paper liners or lightly grease the wells.

In a large mixing bowl, whisk together the eggs, Greek yogurt, almond milk, applesauce, maple syrup, and vanilla extract until smooth and creamy.

In a separate bowl, combine oat flour, protein powder, coconut flour, baking powder, baking soda, and salt. Whisk until evenly distributed.

Gently fold the dry mixture into the wet ingredients until just combined.

In a small bowl, mix coconut sugar with ground cinnamon until well combined. Set aside.

Spoon the muffin batter into the prepared muffin cups, filling them halfway. Sprinkle a layer of the cinnamon-sugar mixture over the batter, then top with more batter until the cups are ¾ full.

Using a toothpick or skewer, gently swirl the batter and cinnamon mixture together in each muffin cup.

Place the muffin tin in the preheated oven and bake for 18-22 minutes until a toothpick inserted comes out clean.

Remove muffins from the oven and let them cool in the pan for about 5 minutes before transferring them to a wire rack.