Preheat oven to 375 degrees. Sprinkle cooking spray on muffin tins.
In a large bowl, thoroughly mix oat flour, baking powder, and salt. Then create a well in the center and add apple, honey, egg, almond milk, and coconut oil.
Mix them together to create a batter. For the topping, combine brown sugar, oat flour, melted coconut oil and cinnamon to form a crumble.
Pour batter into muffin tins and top them up with the crumble. Bake for 30 to 40 minutes or till it is fully done.
Wait for 10 minutes before de-molding the muffins.