This dessert is one of the easiest ones ever, and it includes two shortcuts: canned peaches and cake mix. Similar to a cobbler, it can be out of the oven in less than an hour, and I give different alternatives for making the topping.
I adjusted the recipe to use a whole box of cake mix. It used about half of it, but most readers wrote that they didn't want to be left with an open package. If you already made it as originally posted, use 2 cups of cake mix and ⅔ cup of melted butter. It will have a larger ratio of peaches to topping.
Preheat oven to 350°F (180°C).
Have ready an 8x11-inch or a 9x13 ceramic or glass baking dish.
Dump 30 ounces canned peaches into the dish, spreading to cover the whole surface.
Sprinkle with ½ teaspoon ground cinnamon and drizzle with about ½ to ¾ cup of juice from the can.
For the topping:
Classic topping: Combine 15.25 ounces yellow cake mix with 1 cup unsalted butter, melted, in a medium bowl until you have a crumbly mixture with some dry spots. Top the peaches with this mixture, smoothing it slightly but leaving the edges uncovered. It will not cover them completely, and that is fine. Don't stir or mix it with the peach filling; simply smooth it out a little.
More crumbly topping: In a medium bowl, mix a 15.25 ounces yellow cake mix with ½ cup butter, melted. It should be a thick, drop-biscuit-like mixture, and not pourable or batter-like. If you feel it's too floury, add up to ¼ cup of extra melted butter.
Bake for about 35 to 45 minutes, until golden and dry and the filling bubbles around the edges, checking close to the end of the baking time by carefully lifting the topping to ensure it's fully baked inside. Bake it more if necessary.
Serve warm and plain, with whipped cream or a scoop of vanilla ice cream.
Store leftovers covered or in an airtight container in the refrigerator. Warm slightly before serving in a medium-low oven.
Video
Notes
A 3rd topping option: place thin slices of cold butter over the dry mix (see the 3-ingredient dump cake for reference). It's a very old-fashioned way of making a dump cake, but I feel the melted butter option works better and is easier to prepare. Serving it: as with most fruit and simple desserts, I find the best way is slightly warm with a scoop of vanilla ice cream. But, if that's not possible - because you don't have access to an oven or fridge - it's also really good at room temperature. Adding fresh raspberries or a berry sauce also works well with peaches.To make ahead: bake and then freeze the entire peach dump cake for several weeks. Cover it well with plastic wrap and aluminum foil. To serve, you can thaw it the night or day before in the fridge or warm it in a low oven until the juices bubble up. Warming it: the oven will bring the topping back to its crunchy state, so I don't recommend the microwave, as it won't achieve that. But you can try with a small portion and see how you like it.