Preheat oven to 350°F (175°C). Grease a 9-inch springform pan.
Make the crust: In a bowl, mix graham cracker crumbs, sugar, and melted butter until combined. Press into the bottom of the pan and bake for 8 minutes. Cool completely.
Prepare the rhubarb swirl: In a small saucepan, combine rhubarb, sugar, and lemon juice. Cook over medium heat until thick and soft, about 10–12 minutes. Let cool.
Make the cheesecake filling: Beat softened cream cheese until smooth. Add sugar and vanilla. Beat in eggs one at a time. Stir in sour cream and flour until just combined.
Assemble the cheesecake: Pour half the cheesecake filling over the crust. Add half of the rhubarb swirl and gently swirl with a knife. Repeat with remaining batter and swirl again.
Place the pan in a water bath and bake at 325°F (160°C) for 55–65 minutes, or until the center is slightly jiggly. Turn off the oven, crack the door, and let the cheesecake cool slowly for 1 hour.
Chill in the fridge for at least 4 hours or overnight.
Prepare the raspberry topping: In a small saucepan, combine raspberries, sugar, water, and cornstarch. Simmer until thickened. Let cool, then pour over the chilled cheesecake.