Preheat oven to 375 and spray donut pan with cooking spray.
In a large bowl, whisk together flour, baking powder, sugar, salt, cinnamon and nutmeg.
In a separate bowl, whisk together buttermilk and vanilla extract. Add applesauce and melted butter and whisk until combined.
Pour wet ingredients into dry ingredients and stir until just combined. Fold in grated apple.
The batter will be thick, which is fine!
Fill donut molds about ⅔ of the way full with batter. To make this step really easy, I like to put the batter in a large plastic zip-top bag. Snip a small corner off of the bottom of the bag and pipe the batter into the donut molds.
Bake for about 20 minutes or until donuts are lightly browned.
Allow donuts to cool completely before dusting with powdered sugar and cinnamon.