Preheat oven to 350 degrees, open your cans of pie filing or prepare fresh berries, and spray the pan with nonstick spray.
Place the berries on the bottom of the pan, then evenly sprinkle on the cake mix. Top with thin slices of butter or drizzle with the melted butter. Do not mix.
Bake for about 30 minutes until golden brown and bubbly.
Serve with ice cream or whipped cream, if desired, and enjoy!