Prep the pan and oven: Heat oven to 325°F (163°C). Line an 8x8-inch metal baking pan with parchment, leaving overhang for easy lifting.

Make the crust: In a bowl, combine graham crumbs, sugar, cinnamon, salt, and melted butter. Press firmly into the pan. Bake for 8–10 minutes until lightly set. Cool 5 minutes.

Mix the cinnamon swirl: Stir brown sugar, cinnamon, and melted butter in a small bowl. Set aside.

Beat the filling: With a mixer on medium-low, beat cream cheese until smooth, scraping the bowl. Add sugar and mix until creamy. Blend in sour cream, vanilla, flour, and salt. Add eggs one at a time on low just until combined. Do not overmix.

Assemble: Pour half the cheesecake batter over the crust. Spoon half the cinnamon mixture in small dollops. Add remaining batter, then dot with the rest of the cinnamon mixture. Use a butter knife to gently swirl. Don’t over-swirl.

Bake: Bake 28–35 minutes, until the edges are set and the center has a slight wobble. The top should not be liquid.

Cool and chill: Cool in the pan to room temp, then refrigerate at least 4 hours, preferably overnight, until fully set.

Caramelize the sugar: Sprinkle an even layer of granulated or turbinado sugar over the chilled bars (start with 3 tablespoons). Use a kitchen torch to melt and caramelize the sugar until amber and glassy. Let it harden 3–5 minutes. If you don’t have a torch, place the sugared bars under a hot broiler for 1–2 minutes, watching constantly. Keep the bars cold to protect the cheesecake layer.

Slice and serve: Lift out using parchment. Warm a sharp knife under hot water, wipe dry, and slice into 12–16 bars.