Prep. Preheat the oven to 375°F. Generously grease or line with muffin cups a 12-cup muffin tin.
Toss apples with flour and spices. In a medium bowl, toss 2 cups diced apples, 2 teaspoons flour, and 1/2 teaspoon cinnamon.
Wet ingredients. In a large bowl, whisk together 1/4 cup oil, 1/4 applesauce, and 1 cup sugar until combined. Beat in 2 eggs, 2 teaspoons vanilla, and 1/2 cup buttermilk until well combined.
Dry ingredients. In a small bowl, whisk together the remaining 2 cups flour, 1 1/2 teaspoons baking powder, 3/4 teaspoon salt, 2 teaspoons apple pie spice and 1/2 teaspoon remaining cinnamon. Stir flour mixture into wet ingredients. Fold in the apples.
Bake. Divide batter evenly between the tin cups. Bake 30 minutes, or until a toothpick inserted in the center comes out clean and the edges are golden. Remove pan from oven and place on a cooling rack.
Topping
In a small bowl, stir together 2 Tablespoons sugar and 1 Tablespoon cinnamon. Brush the tops of the muffins with 2-3 Tablespoons melted butter, then roll in the cinnamon-sugar mixture. Serve warm.
Notes
Apples: While I prefer granny smith, honey crisp also works great. If you prefer a softer apple, you can grate the apples instead of having bigger pieces. Mini muffins: You can also bake in a mini muffin pan (makes about 48 mini muffins). For mini muffins bake about 16 to 18 minutes.Apple pie spice: If you don't have apple spice you can use 1 1/4 teaspoon cinnamon, 1/2 teaspoon nutmeg and 1/4 teaspoon all-spice.Storage:Best served warm the first day. Store leftovers in a covered container up to 3 days. Freeze up to 3 months.Recipe updated 8/22