Preheat oven to 350° and grease a muffin pan.
Whisk together all dry ingredients: flour, cinnamon, baking powder and soda, nutmeg, and salt.
In a separate bowl, whisk together applesauce, egg whites, and apple cider vinegar.
Add wet ingredients to dry ingredients and mix just until combined. Do not over-mix. The batter should be pretty light, with some small air bubbles.
Evenly pour batter into the 12 greased cavities of your muffin pan.
Add a heaping 1/2 teaspoon of apple butter to the top of each muffin, then gently swirl with a toothpick. You want the apple butter to be swirled on the top surface of the muffin.
Bake for 15 minutes.
Allow time for the muffins to cool before removing from the muffin pan.