In a large mixing bowl, stir powder cake mix, cinnamon, and pie filling together with a large wooden spoon.
Transfer mixture into 9x13 ungreased glass or ceramic baking dish. (Do NOT grease pan)
Bake for 30 - 35 minutes, or until top is golden brown.
After baking, it is completely normal for your cake to fall in the middle as it cools.
Cut into 12 squares, and top with optional whip cream and additional sprinkles of cinnamon on top. ENJOY!
Notes
For answers to Frequently Asked Questions or tips for common substitutions and variations, please refer to the detailed information above this recipe card.