Preheat your oven to 350°F (175°C).
Grease the bottom and sides of a 9×13 inch baking dish with a small amount of butter or cooking spray.
Pour both cans of apple pie filling into the baking dish and spread them into an even layer using a spoon.
Sprinkle the ground cinnamon evenly over the apple mixture.
Open the box of yellow cake mix and distribute the dry powder evenly over the top of the apples; do not stir the mixture.
Place the thin slices of butter across the entire surface of the cake mix, ensuring as much of the dry powder as possible is covered.
If using nuts, sprinkle them over the top of the butter and cake mix.
Bake for 40 to 45 minutes, or until the top is golden brown and the fruit filling is bubbling around the edges.
Remove from the oven and let it stand for 10 minutes before serving to allow the juices to thicken slightly.