To begin, preheat your oven to 350 and spray a muffin tin with no-stick spray.
In a small mixing bowl, add your dry ingredients and stir them together (oat flour, cinnamon, baking powder, baking soda, and salt).
In a large mixing bowl, add your coconut oil, sugar and applesauce and whisk them together till well combined. Now add in your vanilla and eggs and whisk lightly till combined.
Pour your dry ingredients into your wet ingredients and stir them together till you have a smooth, even batter. Add your apples to your batter and gently fold them in. Fill each muffin tin about 3/4 way full with the muffin batter.
In a small bowl, add your cinnamon sugar topping ingredients and stir them together till well combined. Sprinkle the topping evenly across the tops of your muffins.
Bake in the oven for 15-17 minutes, or till the tops of the muffins are springy to touch and a toothpick inserted comes out clean.
Store these muffins in an airtight container in the fridge, and they taste best within the first 5 days.