Preheat oven to 350°F. Spray a 9x13 baking dish with cooking spray
Pour the 6 cups of cold water into a large mixing bowl.
Add the ¼ cup of lemon juice to the cold water.
Place peeled, cored, and diced apples into the lemon water.
Using a colander, completely drain the diced apples.
Transfer the drained diced apples back into the same large mixing bowl.
Sprinkle the diced apples with the sugars, cinnamon, and apple pie spice. Using a large spoon, toss the apples until well coated.
Pour the coated apples into the buttered 9x13 baking dish, making sure to spread the apples evenly.
Top the apples with the cake mix. Gently shake the pan to help distribute the cake mix.
Arrange the cold butter pats evenly on top of the dry cake mix.
Using a spoon, drizzle the melted butter between the butter pats.
Place the apple dump cake in the oven, and bake for 50 minutes or until the top is golden brown.