Preheat your oven to 375 degrees fahrenheit. Spray a 9x13 inch baking dish with non-stick spray.
Drain one can of peaches completely and pour the fruit into the greased baking dish. Then add the other two cans with all their syrup. Spread the peaches out so they cover the bottom in an even layer.
3 cans sliced peaches
Sprinkle the cinnamon and brown sugar evenly over the peaches.
½ Teaspoons Cinnamon, ⅓ Cup (73 ⅓ g) Brown Sugar
Pour the dry yellow cake mix evenly over the peaches and sugar. Do not stir. Do not mix. Just pour it on and let it sit there.
1 box yellow cake mix
Cut the butter into thin tabs — I aim for about tablespoon-sized pieces — and distribute them as evenly as you can across the top of the dry cake mix. Try to cover the surface so the butter will melt and soak into the mix as it bakes.
½ Cup (113 ½ g) Butter
Bake for 35-40 minutes. The top should be deeply golden with crispy edges where the butter has caramelized the cake mix and sugar. You will hear the fruit bubbling underneath if you listen closely. If the top is browning too fast, tent it loosely with foil for the last 10 minutes.
Let it cool for about 10 minutes before serving. The fruit will be molten hot straight out of the oven. Serve warm with vanilla ice cream or whipped cream if you want.