Piecaken

1. Preheat the oven to 350 degrees F. Spray three 9-inch cake pans with nonstick cooking spray.
2. Mix the cake batters according to the box directions.
3. Pour about 1 cup of the chocolate cake batter in one of the cake pans. Remove the custard pie from its metal tin, put it in the center of the cake pan and gently press it into the batter. Add more cake batter to completely cover the pie but do not fill to the top of the cake pan. Tap the cake pan on the counter to make sure the batter surrounds the pie.
4. Pour about 1 cup of the strawberry cake batter in a second cake pan. Remove the lemon pie from its metal tin, put it in the center of the cake pan and gently press it into the batter. Add more cake batter to completely cover the pie but do not fill to the top of the cake pan. Tap the cake pan on the counter to make sure the batter surrounds the pie.
5. Pour about 1 cup of the vanilla cake batter in a second cake pan. Remove the cherry pie from its metal tin, put it in the center of the cake pan and gently press it into the batter. Add more cake batter to completely cover the pie but do not fill to the top of the cake pan. Tap the cake pan on the counter to make sure the batter surrounds the pie.
6. Bake the cakes until the centers are sturdy when the cakes are gently shaken and the cakes start to pull away from the edges of the pans, 40 to 50 minutes.
7. Let the cakes cool in their pans for 30 minutes, then remove from pans and place the cakes on racks. Let cool completely, about 4 hours.
8. Trim the tops of the cakes with a serrated knife so they are level, making sure not to cut it too far down and cut into the pie.
9. Place the vanilla cake layer on a plate or cake stand. Place the strawberry layer on the vanilla cake layer and then place the chocolate cake layer on top of the strawberry layer.
10. Frost the outside of the cake with the Vanilla American Buttercream.

Vanilla Buttercream:

1. Combine the butter, confectioners' sugar and salt in the bowl of a stand mixer fitted with a paddle attachment (or in a large bowl if using a handheld electric mixer). Mix on low speed until mostly incorporated. Add the vanilla, increase the speed to medium-high and mix until smooth. Adjust the consistency with milk as desired. Use immediately, or refrigerate in an airtight container up to 3 days. Allow to come to room temperature and mix on medium-high until smooth.