2 (16 ounce) cans peaches in heavy syrup
1 (18.25 ounce) package yellow cake mix
½ cup butter
½ teaspoon ground cinnamon, or to taste
Preheat oven to 375 degrees F (190 degrees C).
Empty the peaches into the bottom of a 9×13 inch pan. Cover with the dry cake mixture and press down firmly. Cut butter into small pieces and place on top of cake mixture. Sprinkle top with cinnamon.
Bake at 375 degrees F (190 degrees C) for 45 minutes.