Preheat the oven to 350?F. Grease 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, one at a time, beating until well incorporated. Add 1 1/4 cups sugar, 1/2 cup sour cream, 1 1/2 teaspoons 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, then reduce the heat to 300?F and continue baking until the cake is set in the center, about 30 minutes longer. Remove the cake from the oven and reduce the heat to 250?F.
In a small bowl, combine the remaining 1 1/2 cups of sour cream, remaining 1/4 cup sugar, and remaining 1/2 teaspoon 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 the cheesecake from the oven and cool on a wire rack. When the cake has cooled to room temperature, refrigerate, covered, until ready to serve.
When ready to serve, run a sharp knife under warm water and wipe dry. Run the warmed knife around the edges of the springform pan to release the sides. Remove the springform, slice the cheesecake, and serve.
Makes one 9-inch cheesecake, 10 to 12 servings