Prep Oven & Pan: Preheat oven to 325°F (165°C). Line an 8x8-inch or 9x9-inch metal baking pan with parchment paper, leaving an overhang on the sides for easy lifting.

Make & Bake the Crust: In a medium bowl, stir together graham cracker crumbs, sugar, ground cinnamon, and melted butter until evenly moistened like wet sand. Press firmly into an even, compact layer across the bottom of the prepared pan. Bake for 10 minutes, then remove and let cool slightly while preparing the filling.

Beat the Cream Cheese Base: In a large bowl using an electric hand mixer on low-medium speed, beat the softened cream cheese and granulated sugar together for 2 minutes until completely smooth and lump-free. Beat in the sour cream, vanilla extract, and flour until combined.

Add Eggs Gently: Add eggs one at a time, mixing on low speed just until incorporated. Do not overmix or whip air into the batter, which can cause cracking.

Create the Pumpkin Swirl: Scoop out 1 cup of the plain cheesecake batter and place it into a separate small bowl. Stir in the pure pumpkin purée, pumpkin pie spice, and brown sugar until thoroughly combined and glossy.

Layer & Marble: Pour the remaining plain cheesecake batter over the baked crust and smooth evenly with an offset spatula. Drop dollops of the spiced pumpkin batter across the top. Drag the tip of a butter knife or wooden skewer gently through the batter in figure-eight loops to create a gorgeous marbled swirl pattern.

Bake to Set: Bake at 325°F (165°C) for 32-36 minutes, until the edges are set and lightly puffed, but the center still has a gentle wobble when the pan is nudged. Turn off the oven, crack the door open, and let the cheesecake rest inside for 20 minutes to prevent thermal shock.

Chill, Slice & Serve: Remove to a wire cooling rack and cool completely to room temperature (about 1 hour), then transfer to the refrigerator to chill for at least 3 hours (or overnight) until firm. Use parchment overhang to lift from pan, slice into 16 neat squares with a warm sharp knife, and enjoy!