Preheat oven to 150°C (300°F). Place the flour, sugar and butter in a bowl and rub with your fingertips to form a rough dough. Using the back of a spoon, press the mixture into the base of a lightly greased 20cm round springform tin lined with non-stick baking paper. Bake the base for 30 minutes or until golden and just cooked. Set aside. To make the filling, place the cream cheese, ricotta, eggs, sugar, lemon juice and rind, and vanilla in a food processor and process until smooth. Place the cornflour and water in bowl and mix until smooth. Add the cornflour mixture to the cheese mixture and mix to combine. Pour over the cooked base and bake for 1 hour and 10 minutes or until light golden and just set. Turn the oven off and allow to cool in the oven with the door closed. Refrigerate for 1 hour or until cold. Top with the cream to serve. Serves 8–10.