1 1/2 teaspoons pumpkin pie spice or add more to your liking
1/2 cup powdered sugar
Preheat oven to 350°F. Move the oven rack to the lowest rack.
In a stand mixer or with a hand mixer, beat the cake mix, flour, pumpkin, spice and water on low speed 30 seconds. Then beat it on medium speed 1 minute. Pour the batter into an ungreased 10-inch angel food cake pan.
Bake 37 to 47 minutes or until crust is dark golden brown and cracks are dry. Remove the cake from the oven and immediately turn the pan upside down onto a glass bottle or support it with glass cups. Let it sit upside down for about 2 hours or until cake is completely cool. Using a knife, loosen the cake from the sides of the pan and invert the cake to a serving plate. Use a long serrated knife to cut the cake in half horizontally to make two layers.
For the frosting, fold together the Cool Whip, pumpkin pie spice and powdered sugar in a bowl. Spread half of the frosting on top of one of the cake layers. Then place the other cake layer on top. Top the cake with the remaining frosting.