Preheat & Prep: Preheat your oven to 350°F (175°C). Generously grease a 9x13-inch baking dish with non-stick cooking spray.

Mix the Cake Batter: In a large mixing bowl, combine the dry angel food cake mix, dry pistachio pudding mix, vegetable oil, eggs, and the entire can of crushed pineapple (including the juices). Beat with a hand mixer on medium speed until the ingredients are well combined and the batter is smooth.

Bake: Pour the batter into your prepared baking dish, spreading it out evenly. Bake for 30 to 35 minutes, or until a toothpick inserted into the center of the cake comes out clean.

Cool: Remove the cake from the oven and allow it to cool completely in the pan on a wire rack. (Do not attempt to frost a warm cake!)

Prepare the Frosting: While the cake is cooling, make the frosting. In a medium bowl, whisk together the second box of instant pistachio pudding mix and the cold milk until the mixture begins to thicken.

Fold & Combine: Gently fold the thawed Cool Whip into the pudding mixture until fully combined and fluffy.

Frost & Chill: Spread the frosting evenly over the completely cooled cake. Place the cake in the refrigerator to chill for at least 2 hours before serving to allow the frosting to set.

Garnish & Serve: Right before slicing, sprinkle the top of the cake with chopped pistachios. Enjoy!