Mix crumbs with 3 tablespoons of melted butter and 3 tablespoons of sugar.
Press crumb mixture onto bottom of 9inch springform pan(I use the bottom of a glass to press it firmly).
Bake this for 10 minutes.
Beat cream cheese,3/4 cup of sugar,lemon juice and zest and 1/2 teaspoon of vanilla until well blended.
Add eggs one at a time, mixing on low after each one just until blended.
Pour over prebaked crust.
Bake for 55 minutes to 1 hour until middle is almost set.
Meanwhile while that is baking, mix the sour cream with remaining vanilla and sugar until well blended.
When middle of cake is almost set remove from oven and carefully spread the sour cream mixture over the top and put back in the oven for an additional 10 minutes. Remove from oven and run a thin bladed knife around the rim to loosen the cake. COOL FULLY before removing pan rim. Refrigerate for at least 4 hours before serving.