Preheat the oven to 325°F (163°C). Line an 8-inch or 9-inch square baking pan with parchment, leaving overhang for easy lifting.

Make the crust: In a bowl, mix graham crumbs, sugar, melted butter, and a pinch of salt until evenly moistened. Press firmly into the pan, packing it tightly. Bake for 8–10 minutes. Set aside to cool slightly.

Make the blueberry swirl: In a small saucepan, combine blueberries, sugar, and lemon juice over medium heat. Cook 4–6 minutes, stirring and gently smashing some berries.

Stir in the cornstarch slurry and cook 30–60 seconds until thick and jammy. Remove from heat and cool to room temperature.

Make the cheesecake filling: Beat cream cheese and sugar on medium speed until smooth and fluffy, about 2 minutes. Scrape the bowl.

Add eggs one at a time, mixing on low just until combined. Add sour cream, vanilla, lemon juice, lemon zest, and a pinch of salt. Mix on low until silky and no lumps remain. Avoid overmixing.

Assemble: Pour the cheesecake batter over the crust and smooth the top. Dollop spoonfuls of blueberry sauce over the surface and swirl gently with a knife or skewer.

Bake for 28–35 minutes, until edges are set and the center has a slight jiggle. Don’t bake until firm.

Cool in the pan on a rack for 1 hour, then refrigerate at least 4 hours, preferably overnight, until fully set.

Lift out using the parchment and slice into bars. Wipe the knife between cuts for clean edges.