Preparation : Beat egg whites until frothy; add cream of tartar and beat until stiff; gradually beat in 1/2 cup sugar. Spread in well greased 9 inch pie tin. Bake 20 minutes in 275 degree oven, then 40 minutes at 300 degrees. Beat egg-yolks until lemon-colored; gradually add sugar, then milk, lemon juice and rind. Cool until thick, stirring constantly; cool. Spread 1/2 the whipped cream over cooled meringue, then spread lemon custard on, then rest of whipped cream. Refrigerate 24 hours before serving.