1. Prepare the Raspberry Filling

To begin, we’ll make the raspberry filling, which will create those beautiful, vibrant swirls in the cheesecake. Start by mixing the cornstarch, lemon juice, and warm water in a small bowl. Whisk them together until the cornstarch is fully dissolved. In a medium saucepan, combine the raspberries and sugar. Heat over medium heat while stirring continuously for about 3 minutes. This will release the juice from the raspberries. Add the cornstarch mixture to the saucepan and cook for another 3 minutes, mashing the raspberries as they cook. The mixture should bubble slightly and thicken. Once it has thickened, pour the mixture into a food processor and puree it until smooth. Then, strain it through a fine sieve to remove the seeds. Set the puree aside to cool.

2. Prepare the Crust

Preheat your oven to 325°F (163°C). Line a 9-inch springform pan with parchment paper and grease the sides. In a small bowl, combine the graham cracker crumbs, melted butter, and sugar. Mix until the crumbs are evenly coated. Press the mixture into the bottom of the springform pan and slightly up the sides. Bake the crust for 10 minutes, then remove it from the oven and set it aside to cool.

3. Make the Lemon Cheesecake Filling

Reduce your oven temperature to 300°F (148°C). In a large mixing bowl, beat the cream cheese, sugar, and flour on low speed until the mixture is smooth and fully combined. Scrape down the sides of the bowl to ensure everything is incorporated. Next, add the sour cream, lemon juice, and lemon zest, mixing on low speed until well combined. Add the eggs one at a time, mixing slowly after each addition. Then, add the egg yolks and continue mixing until smooth. Scrape down the sides of the bowl as needed to make sure everything is well mixed.

4. Assemble the Cheesecake

To add the raspberry swirl, spoon two tablespoons of the cheesecake filling into the cooled raspberry puree and mix it in. This will help the raspberry swirl incorporate better into the cheesecake. Pour about 3/4 of the cheesecake filling into the crust. Then, drop spoonfuls of half of the raspberry filling on top. Use a knife or spatula to swirl the raspberry filling through the cheesecake. Add the remaining cheesecake filling on top and gently spread it evenly. Drop the remaining raspberry filling on top and swirl it again with a knife or spatula.

5. Bake the Cheesecake

To prevent cracks, we’ll use a water bath. Place the springform pan into a larger pan, and fill the outer pan with warm water, making sure the water comes halfway up the sides of the springform pan but does not cover the top edge of the foil. Bake the cheesecake for 1 hour 25 minutes. The center should be set but still slightly jiggly. Turn off the oven and leave the cheesecake in the oven with the door closed for 30 minutes. This gradual cooling process helps prevent cracking. After 30 minutes, crack the oven door open for another 30 minutes to allow the cheesecake to cool further.

6. Chill and Serve

Once the cheesecake has cooled, remove it from the oven and the water bath. Place it in the refrigerator for at least 4 hours, or preferably overnight, to allow it to set. When you’re ready to serve, remove the cheesecake from the springform pan and place it on a serving dish. Top it with fresh raspberries and lemon slices. This cheesecake is best enjoyed within 3-4 days.