Preheat the oven to 350 degrees F.
Butter a 9-inch springform pan with the butter and coat it with the bread crumbs, shaking out any excess.
Press the ricotta through a fine sieve and combine it with the cream cheese in the bowl of an electric mixer. Beat on medium speed until very smooth, about 5 minutes. Add the eggs, 1 at a time, beating until well incorporated. Add 1 1/4 cups of the sugar, 1/2 cup of the sour cream, 1 1/2 teaspoons of the vanilla, and the lemon zest and beat until very smooth and light, 2 to 3 minutes.
Pour the batter into the prepared springform pan. Bake for 45 minutes and then reduce the heat to 300 degrees F and continue cooking until the cake is set in the center, about 30 minutes longer. Remove the cake from the oven and reduce the heat to 250 degrees F.
In a small bowl combine the remaining 1 1/2 cups of sour cream, remaining sugar, and remaining vanilla. Stir until the sugar is dissolved. Pour this mixture over the top of the cheesecake and smooth with the back of a spoon or a spatula so that the sour cream mixture evenly covers the top of the cake. Return to the oven and bake for 10 minutes.
Remove from the oven and cool on a wire cooling rack. When the cake has cooled to room temperature, refrigerate, covered, until ready to serve. When ready to serve, run a sharp knife around the edges of the springform pan to release the sides. Slice the cheesecake with a warm knife and serve.
![]("/food/images/spacers/spacer.gif"){kind=spacer}
