Make the Crust : Preheat the oven to 325°F (163°C). In a mixing bowl, combine the graham cracker crumbs and melted butter. Mix until evenly moistened. Press the mixture firmly into the bottom of a 9-inch springform pan. Bake the crust for 8-10 minutes, then set aside to cool.

Prepare the Raspberry Swirl : In a small saucepan over medium heat, combine the raspberries and 1 tablespoon of sugar. Cook until the raspberries break down and form a thick sauce, about 5-7 minutes. Strain the mixture through a fine mesh sieve to remove seeds. Set the smooth raspberry sauce aside to cool.

Make the Cheesecake Filling : In a large bowl, beat the softened cream cheese and sugar together until smooth and creamy. Add the sour cream, lemon juice, and lemon zest. Mix until combined. Beat in the eggs, one at a time, mixing just until incorporated. Do not overmix, as it can create air bubbles.

Assemble the Cheesecake : Pour the cheesecake filling over the prepared crust, smoothing the top with a spatula. Drizzle the raspberry sauce over the top in small spoonfuls. Use a toothpick or skewer to swirl the sauce into the batter, creating a marbled effect.

Bake the Cheesecake : Place the springform pan on a baking sheet and bake in the preheated oven for 55-65 minutes. The center should be slightly jiggly but set. Turn off the oven, crack the oven door, and let the cheesecake cool inside for 1 hour.

Chill and Serve : Once the cheesecake reaches room temperature, refrigerate it for at least 4 hours, preferably overnight, to set completely. Before serving, garnish with fresh raspberries or lemon slices if desired.