Preheat oven to 375 degrees. In a small saucepan, melt the butter. Stir in the crumbs and sugar. Pat crumbs firmly on the bottom of a buttered springform 9 inch pan. Bake 7 minutes. Cool while preparing the filling. Reduce oven temperature to 300 degrees. In a large mixing bowl, beat cream cheese until light and fluffy. Add condensed milk and the egg yolks. Beat until smooth. Stir in the lemon juice. Set aside. In a small bowl, beat egg whites with salt to soft peaks. Fold into the sweetened condensed mixture. Turn into the prepared pan. Bake 50 - 55 minutes. (fruit topping is optional)
