Preheat the oven to 350° F. Lightly grease an 10.25-inch cast iron skillet. Pour the cans of pie filling into the bottom of the skillet. In a medium bowl, stir together the cake mix, melted butter, and cinnamon. Drop the batter by dollops on top of the filling. Bake for 50 to 60 minutes or until the batter is set. Serve warm.