In a small bowl, combine graham cracker crumbs and melted butter. Press onto the bottom of a 9x13-inch baking dish coated with cooking spray.
Bake at 325° for 10-12 minutes or until set. Cool on a wire rack.
In a large bowl, beat the cream cheese until smooth. Beat in eggs, one at a time, just until blended. Add the sugar and vanilla, beat on low speed until mixture is smooth.
Spread half of the cheesecake batter into the cooled baking dish, smoothing the top, and set aside.
Add the pumpkin purée and pumpkin pie spice to the remaining filling and whisk until smooth and combined. Carefully spread pumpkin mixture over plain cheesecake mixture into an even layer.
Bake at 325° until the edges are set but the center still jiggles slightly, 40 to 50 minutes.
Place the dish on a wire rack and cool completely, 2 to 3 hours. Cover with aluminum foil and refrigerate at least 3 hours or overnight.
Cut into bars, garnish with whipped cream and pumpkin pie spice if desired.