Preheat oven to 375 degrees. Pour one can of peaches (syrup and all) into a 9x13 glass baking dish. Drain the second can of peaches, reserving the syrup, and pour the peaches into the pan.
Sprinkle the dry cake mix and ground cinnamon over the peaches and level the top.
Drizzle with melted butter and reserved syrup, doing your best to cover all the cake mix with liquid.
Bake 35-45 minutes or until the top is puffed and browned. Cool 10 minutes before serving with whipped cream or vanilla ice cream.