Prep the pan: Heat oven to 325°F (163°C). Wrap the outside of a 9-inch springform pan with two layers of foil to prevent leaks if using a water bath. Lightly grease the inside.

Make the crust: Stir graham crumbs, sugar, salt, and melted butter until the mixture resembles damp sand. Press firmly into the bottom and slightly up the sides of the pan. Bake for 8–10 minutes. Cool while you make the filling.

Cook the blueberry swirl: In a small saucepan, combine blueberries, sugar, lemon zest, and lemon juice. Cook over medium heat until berries burst and release juices, about 5–7 minutes. Stir in cornstarch slurry and cook 1–2 minutes until thickened. Cool to room temperature, then puree or mash for a smoother swirl.

Beat the filling: Using a mixer on medium-low, beat cream cheese and sugar until smooth and no lumps remain, scraping the bowl often. Mix in sour cream, lemon zest, lemon juice, vanilla, and salt.

Add eggs gently: Add eggs one at a time on low speed, mixing just until combined. Do not overmix; too much air causes cracks.

Assemble: Pour half the cheesecake batter over the crust. Spoon half the blueberry sauce in dollops. Swirl lightly with a knife. Add remaining batter and repeat with remaining sauce. Swirl again with a gentle hand.

Bake with a water bath (recommended): Place the pan in a larger roasting pan. Pour hot water into the roasting pan until it reaches halfway up the springform. Bake 55–70 minutes, until edges are set and the center wobbles like Jell-O.

Cool slowly: Turn off the oven, crack the door, and let cheesecake rest inside for 45–60 minutes. Remove from the oven and water bath. Run a thin knife around the edge to loosen. Cool to room temperature, then chill at least 6 hours or overnight.

Serve: Remove the ring, slice with a hot, clean knife, and wipe between cuts. Garnish with fresh blueberries and lemon zest if you like.