1-First Step: Whisk dry ingredients. In a bowl, sift together 2 1/2 cups flour, 2 tsp baking powder, 1/2 tsp baking soda, 1 tsp cinnamon, 1/2 tsp nutmeg, and 1/2 tsp salt.

2-Second Step: Cream butter and sugar. Beat 1 cup softened butter with 2 cups sugar until light and fluffy, about 3 minutes. Add 4 eggs one at a time, then 1 tsp vanilla.

3-Third Step: Alternate wet and dry. Mix in dry ingredients alternately with 1 cup buttermilk, starting and ending with dry. Fold in 2 cups diced apples gently. Divide batter evenly among pans.

4-Fourth Step: Bake the layers. Place pans in oven for 25-30 minutes, until a toothpick comes out clean. Cool in pans 10 minutes, then transfer to racks.

5-Fifth Step: Cook the filling. In a saucepan over medium heat, combine 4 cups sliced apples, 1/2 cup brown sugar, 2 tbsp cornstarch, 1 tsp cinnamon, and 1/4 cup butter. Stir until thickened, about 10 minutes. Cool completely.

6-Sixth Step: Make frosting. Beat 8 oz cream cheese and 1/2 cup butter until smooth. Gradually add 4 cups powdered sugar and 1 tsp vanilla. Beat until spreadable.

7-Seventh Step: Assemble the cake. Level cooled layers if needed. Place first layer on plate, spread 1/3 apple filling, top with second layer, repeat. Frost top and sides generously.

8-Final Step: Chill 30 minutes to set. Garnish with apple slices or cinnamon. Slice and serve.