Place ricotta cheese, sour cream, cream cheese, sugar and butter into
a large mixing bowl. Add flour, eggs, cornstarch, vanilla and lemon
juice. Beat with electric mixer: start on low speed, move to medium
and finish with about 10 minutes on high speed.
Batter should be smooth and liquid. Grease and lightly flour a
10-inch round baking pan by 3-inches deep. Pour batter into the pan
and bake 1 hour in a preheated 350 degree F oven.
Leave cake in oven with door closed, for an additional hour after the
heat is turned off. Then cool on rack and refrigerate for storage.
Makes 20 servings.