Preheat & Prep:
Preheat oven to 325°F (163°C). Wrap a 9-inch springform pan in foil and lightly grease it.

Make the Crust:
Mix graham cracker crumbs, sugar, and melted butter until combined. Press firmly into the bottom of the pan. Bake for 10 minutes and let cool.

Make Raspberry Swirl:
In a saucepan, heat raspberries and sugar over medium heat. Mix cornstarch and lemon juice in a small bowl; stir into raspberries. Cook until thickened. Strain to remove seeds and cool completely.

Prepare Filling:
Beat cream cheese on low until smooth. Add sugar and flour, then sour cream, lemon juice, and zest. Mix in eggs one at a time until just combined.

Assemble:
Pour half the cheesecake batter into the crust. Spoon half the raspberry puree on top and swirl gently. Add the remaining batter and swirl the rest of the raspberry sauce.

Bake:
Place the pan in a water bath (in a large roasting pan filled halfway with hot water). Bake at 300°F (148°C) for about 1 hour 25 minutes, until the edges are set and the center jiggles slightly.

Cool:
Turn off the oven, crack the door, and let the cheesecake cool inside for 1 hour. Then cool to room temperature and refrigerate at least 6 hours or overnight.

Serve:
Slice with a warm knife, wipe between cuts, and garnish with fresh raspberries and lemon zest.