1.Preheat oven to 350 degrees, lightly spray a 13 x 9 baking pan with cooking spray.
2.Empty pie filling into pan and with a rubber spatula, spread evenly over the bottom of pan.
3.In a medium to large mixing bowl, add cake mix with can of seltzer, baking powder, and vanilla extract. Using a whisk, mix until combined. It does not have to be completely combined. There can be some lumps. Pour over pie filling. Dot with butter cubes. Bake for about 29 to 32 minutes. Check after 29 minutes. If testing with a toothpick, don’t go down to bottom because of the pie filling. Should have no crumbs or dry crumbs.
4.Let cool on counter for at least an hour, Place in fridge and cool completely. When chilled, spread Cool Whip and place back in fridge for a couple of hours.