Preheat oven to 350 degrees F.

2, Using an electric mixer at medium speed, mix cottage cheese, sugars, egg whites, vanilla and lemon zest until very smooth. 

 Pour batter into a lightly grease a 9-inch spring form pan. Bake in a 350-degree oven for 40-50 minutes or until just jiggly in the center. The cake will finish cooking from the retained heat after you take it out of the oven. 

 Chill in refrigerator overnight or for at least 4 hours before slicing and serving. 

 Before serving top with either a layer of low fat sour cream or your favorite pie filling, if desired.