Base Layer: Pour both cans of sliced peaches along with their juices directly into an ungreased 9x13-inch baking dish, spreading them into an even layer.
Spice Infusion: Dust the ground cinnamon and ground nutmeg evenly over the top of the peach layer.
Cake Layer: Shake the dry cake mix evenly over the spiced peaches, covering them completely. Use a spatula to smooth the powder into a flat surface, but do not stir it into the fruit.
Butter Layer: Slice the cold butter into thin, even pieces and arrange them neatly across the dry cake mix to cover as much area as possible.
Bake: Bake uncovered in a preheated oven at 350°F (175°C) for 45 minutes, until the fruit juices bubble at the edges and the crust turns a beautiful golden brown.
Rest: Remove from the oven and let the cake sit for 15 minutes at room temperature to cool and set slightly before serving.