Heat the oven to 350°F (175°C) and grease a 9 x 13-inch baking dish. Use a shallow baking dish of this size so the fruit and topping cook evenly.

Spread both cans of apple pie filling evenly across the bottom of the prepared dish. Sprinkle the cinnamon over the apples if using it.

Sprinkle the dry cake mix evenly over the apple filling. Do not stir the cake mix and apples together, because the separate layers create the proper fruit-to-topping texture.

Pour the melted butter slowly over the entire surface of the cake mix, covering as much of the dry mix as possible. You can also arrange thin slices of cold butter over the top instead.

Scatter the chopped pecans or walnuts over the buttered cake mix if desired. The nuts add a pleasant crunch and pair especially well with spice cake mix.

Bake for 45–50 minutes, until the top is golden brown and the apple filling is visibly bubbling around the edges. Check the dish near the end of the baking time so the topping does not become overly dark.

Let the dump cake rest for 10–15 minutes before serving. Spoon it into bowls while warm and add vanilla ice cream or whipped cream if desired.