Start by oiling an 8X13 glass pan.
Preheat oven to 375 F ( 190 C)
Spread the pie filling can evenly on the bottom. You can use a medium or big can, depending on how much filling you want. A small can won't have enough in there.
Get the cake mix box and spread that evenly in the middle. Use your hand or a rubber spatula to even it out.
Melt the butter and spread that evenly on top, making sure to cover every part of it.
This pie is so delicious, that there won't be leftovers for long, and you will be asked for the recipe!