2 (16 ounce) cans peaches in heavy syrup
1 (18.25 ounce) package yellow cake mix
1/2 cup butter
1/2 teaspoon ground cinnamon, or to taste
Preheat oven to 375 degrees F.
Empty peaches into the bottom of one 9×13 inch 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 375 degrees F for 45 minutes.