Preheat oven to 350F. Line a 9x13-inch baking pan with parchment or foil, and spray with nonstick spray.

Prepare the crust: add graham cracker crumbs to a food processor and pulse until fine. Mix with melted butter until crumbly. Press into the prepared baking pan to form an even crust.

Bake the crust for 10 minutes, then set aside to cool slightly.

Make the pumpkin mixture: whisk pumpkin puree, pumpkin pie spice, cinnamon, flour, and salt in a large bowl.

In a separate bowl, beat cream cheese and sugar until smooth. Add sour cream and vanilla, mix well. Incorporate eggs one at a time, mixing just until combined.

Remove 1.5 cups of cream cheese mixture; add it to the pumpkin mixture and stir until just combined.

Drop spoonfuls of pumpkin mixture onto cream cheese batter in the crust. Alternate with spoonfuls of the remaining cream cheese mixture.

Use a toothpick or knife to swirl the two batters together to create a marbled effect.

Bake for 40 minutes, until set. Cool in pan for 1 hour, then chill in the fridge for at least 2 hours or overnight.

Slice and serve chilled, topped with whipped cream or caramel if desired.