Preheat oven to 350 degrees.
Grease a 9x13 baking dish.
Add pie filling and spread to cover the bottom of the dish.
Sprinkle entire box of cake mix on top of pie filling.
Place pats of butter on top of the cake mix, covering as evenly and as much of the cake as possible.
Bake for 40 minutes. A toothpick or knife inserted in the center should come out mostly clean (there may be a little of the pie filling on it).
Serve warm. Tastes best warm or at room temperature but leftovers may be stored in the refrigerator for 3-4 days.