Preheat the oven to 325 degrees F (165 degrees C) with an oven rack in the middle position.

Beat cream cheese, ricotta cheese, and sugar in a large bowl with an electric mixer until well combined. Beat in eggs, one at a time. Add butter, flour, cornstarch, and vanilla extract; beat until well combined. Fold in sour cream and lemon juice; pour into an ungreased 10-inch springform pan.

Bake in the preheated oven for 1 hour. Turn off oven; leave cheesecake inside the oven for 2 hours. Remove cheesecake from the oven; cool completely.

Run a thin spatula around edges of pan before opening pan to remove cheesecake. Serve cold or at room temperature; refrigerate leftovers.