Preheat the oven to 350 degrees F. Line a muffin tin with paper liners and set aside.
In a medium-sized bowl, whisk together the flour, salt, cinnamon, and baking powder. Set aside.
In another medium-sized bowl, whisk together the coconut oil, brown sugar, eggs, oatmeal, and applesauce.
Add the dry ingredients to the wet and stir until just combined. Add the apple and stir until combined.
In a small bowl, combine the flour, oats, brown sugar, walnuts, and cinnamon. Work the butter into the dry ingredients until it resembles wet sand.
Bake for 13-15 minutes, or until a toothpick, when inserted into the center, comes out clean. Allow the muffins to cool in the tin for 5 minutes before removing them to a wire rack to finish cooling.
Notes: I used a Gala apple and left the skin on