• Preheat the oven to 350℉. Lightly spray the bottom of a 9x13 baking pan with cooking spray, or line it with parchment paper. Set aside. 

Make The Graham Cracker Crust

• Place the cinnamon graham crackers into a food processor and pulse for about 30 seconds or until well crushed in fine crumbs.  Add in the sugar and melted butter. Pulse again until thoroughly combined and it's the consistency of wet sand. 
  15 whole cinnamon graham crackers, 3 tablespoons granulated sugar, 1/2 cup (1 stick) salted butter
• Firmly press the graham cracker crust mixture into the bottom of the prepared pan, in an even layer. Use your fingers or the bottom of a measuring cup to really pack it in tight. 
• Cover the pan with plastic wrap, or a lid, and place it in the freezer while you prepare the cheesecake layer. 

Make The Pumpkin Cheesecake

• In a small bowl, stir together the pure pumpkin and pumpkin pie spice. Set aside. 
  1 cup pure pumpkin, 1½ teaspoons pumpkin pie spice
• In a separate larger mixing bowl, using a hand electric mixer or stand mixer, beat the cream cheese and powdered sugar on medium speed until well combined, smooth, and creamy - about 2 minutes. 
  3 bars (8 oz each) full-fat cream cheese, 1 cup powdered sugar
• Add in the sour cream and vanilla. Beat just until combined.
  1/3 cup sour cream, 1½ teaspoons vanilla extract
• Add in the eggs, making sure to beat just until they're incorporated. Cheesecake mixture should look smooth and glossy. 
  3 large eggs
• Remove half of the cheesecake batter from the bowl and add it into the pure pumpkin mixture (set aside from earlier). Stir until it's well combined. 

Assemble & Bake Cheesecake Bars

• Remove the crust from the freezer. Pour the cheesecake batters carefully onto the crust by using a large spoon, and alternating spoonfuls of the pumpkin cheesecake mixture and then the plain cheesecake mixture inside the pan on top of the crust. 

  ^{* Alternate the batters into the pan so it makes a checkered pattern of the two different batters. See pics above in post for example.}
• Use a table knife/butter knife, to gently swirl both batters together but making sure that you do not cut into the crust. 
• Bake for 35-40 minutes or until the sides are set and pulled slightly away from the pan, and the center is mostly set but still slightly wobbly. 
• Remove the cheesecake bars from the oven and allow them to cool completely, at room temperature, before refrigerating. 
• Once cooled, cover the pan with plastic wrap, aluminum foil, or a lid and refrigerate for at least 6-8 hours, but overnight is preferred (closer to 12 hours). 
• Serve the pumpkin cheesecake bars chilled from the fridge. Garnish with whipped cream, caramel sauce, mini chocolate chips, crushed cinnamon graham crackers, finely chopped pecans etc. Or eat them as is!