Preheat the oven to 350°F
Grease a 9×13-inch baking dish
Pour 2 cans of sliced peaches with syrup into the dish
Add 1 teaspoon cinnamon if desired
Sprinkle 1 box of yellow cake mix evenly over the peaches
Cut 1 cup of butter into thin slices and place over the cake mix
Bake for 45 to 50 minutes until golden and bubbly
Let cool for 10 to 15 minutes before serving