• Adjust oven rack to center of oven and preheat oven to 350°F. Lightly spray a 9" x 13" baking dish with nonstick baking spray and set aside.

Apple Filling

• Add prepared apple slices to prepared 9" x 13" baking dish, in an even layer. Sprinkle lemon juice evenly over apples, then fold a few times to incorporate. Spread apples into an even layer.
• Sprinkle brown sugar evenly over apples, followed by apple pie spice, and then cornstarch. Fold to evenly incorporate. Spread apples into a very even layer, arranging the apple pieces to fill in any gaps, etc. With a paper towel, wipe interior sides of baking dish for a cleaner finished appearance.

Cake Layer

• Add dry cake mix and apple pie spice to a medium mixing bowl; whisk to incorporate. Sprinkle mixture evenly over apple filling, then use a spatula to lightly even-out the mixture so it's level across the entire pan. Do not press on the dry mixture while doing so.
• In a liquid measure with a spout, melt ¾ cup (1½ sticks) of the butter. Very slowly drizzle the melted butter over the top of the dry cake mixture, to cover as much of the dry cake mixture as possible.
• Then slice off very thin pieces of the remaining ½ stick of butter (it helps if the butter is cold) and place on any spots of dry cake mixture. If you like the dry cake mix bites from a traditional dump cake, you can skip this step!
• Bake 55 minutes, or until apples are lightly thickened, glossy, and bubbling at the edges, and the cake batter topping is nicely browned.
• This easy dessert is best enjoyed on the day it is made, although it keeps perfectly well if you want to make it 6-8 hours in advance >> I recommend that you not cover the pan; just let it sit at cool room temperature uncovered. Our family especially likes to eat this while it's still a bit warm, about 25-30 minutes after it comes out of the oven - and with scoops of vanilla ice cream, of course!