1 (18.5 ounce) package yellow cake mix
2 (16 ounce) cans peaches in heavy syrup
1/2 cup butter
1/2 tsp. ground cinnamon, or to taste
Preheat oven to 375F.
Empty peaches into the bottom of one 9x13" pan.
Cover with the dry cake mix and press down firmly.
Cut butter into small pieces and place on top of cake mix.
Sprinkle top with cinnamon.
Bake at 375F for 45 minutes.