Preheat the oven to 325°F (160°C). Grease a 9-inch springform pan.
In a mixing bowl, combine graham cracker crumbs, sugar, and melted butter. Press the mixture into the bottom of the prepared pan.
In another bowl, beat cream cheese and ricotta cheese until smooth. Add sugar and beat until creamy.
Beat in eggs, one at a time, until well combined. Add sour cream, lemon zest, lemon juice, and vanilla extract, and beat until smooth.
Pour the batter over the crust in the springform pan.
Place the pan on a baking sheet and bake in the preheated oven for 60-70 minutes, or until the edges are set and the center is slightly jiggly.
Turn off the oven and leave the cheesecake inside with the door closed for 1 hour.
Remove the cheesecake from the oven and let it cool completely. Refrigerate for at least 4 hours or overnight before serving.
Serve chilled and garnish with lemon slices or whipped cream if desired.