Lighter than most cheesecakes, this rises and browns slightly while cooking, giving it a very special appearance. Tastes best if made a few days ahead of time.
Have butter at room temperature. With hands, mix flour with butter until blended. Add egg yolk and sugar and blend, again. Press half of pastry onto the bottom of 9-inch springform pan. (Butter fingers to prevent sticking.) Bake at 400 degrees F for 8 to 10 minutes or until lightly browned. Cool. Press remaining pastry along side of the rim, going about halfway up. Refrigerate while making the filling.
Have cheese and eggs at room temperature. Cream cheese until it is soft. Add flour and sugar; mix well. Beat in egg yolks, sweet and sour cream, and vanilla. Beat egg whites with salt until stiff but not dry. Fold into cheese mixture. Pour into prepared crust. Bake at 350 degrees F for 50 minutes or until firm. Turn oven off but leave cheesecake in oven for half an hour with door slightly open. Remove and allow to cool for at least 1 hour before refrigerating. Top with favorite fruit topping.