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. Using a whisk, mix until combined. It does not have to be completely combined. There can be some lumps. Add vanilla extract. Mix again then, 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 completely. Spread Cool Whip and place in fridge for a couple of hours. Add lemon zest to top of Cool Whip. Slice up and Enjoy!