Preheat the oven to 350 degrees F. Spray a 13-by-9-inch baking pan with nonstick cooking spray.
For the crust: In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with an electric mixer, combine the cake mix, pumpkin pie spice, eggs and vanilla and beat on medium speed until well combined, about 1 minute. Add the butter and mix just until combined. Spread the mixture evenly in the prepared baking pan.
For the filling: In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with an electric mixer, beat the cream cheese until smooth, about 2 minutes.. Add the eggs, pumpkin pie spice and vanilla and beat until smooth and creamy. Add the pumpkin and butter and beat until fully incorporated. Add the powdered sugar and beat on low speed to incorporate, and then beat on medium until light and smooth, about 1 minute. Pour over the crust layer and smooth the top with a spatula.
Bake until the edges are puffed and golden brown and the center is set, about 40-45 minutes. Let cool completely on a wire rack. Cut into squares and serve topped with whipped cream.
Refrigerate any leftovers.
Notes
Betty Crocker is my preferred brand of cake mix.Adapted from Food Network