For the crust: Preheat the oven to 325°F (163°C). In a medium bowl, mix together the graham cracker crumbs and sugar. Add the melted butter and stir until the crumbs are well-coated and the mixture is damp. Press the mixture into the bottom of a 9-inch springform pan, creating an even layer. Bake for 8-10 minutes and then cool.

1. For the cheesecake filling: In a large bowl, combine the ricotta cheese, cream cheese, and sugar. Beat until smooth and creamy. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract, lemon zest, sour cream, and flour, mixing until well combined. Pour the cheesecake mixture over the cooled crust and smooth the top.
2. Bake the cheesecake: Bake for 50-60 minutes, or until the edges are set and the center is slightly jiggly. Turn off the oven and let the cheesecake cool in the oven for 1 hour with the door ajar. Then, refrigerate for at least 4 hours or overnight to set.
3. For the raspberry compote: In a small saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat until the raspberries break down. If desired, add cornstarch to thicken. Let the compote cool to room temperature.
4. To assemble: Once the cheesecake has set, remove it from the springform pan and place it on a serving plate. Spoon the raspberry compote generously over the top of the cheesecake and optionally garnish with fresh raspberries or powdered sugar.