Beat egg whites and cream of tartar until soft peaks form. Slowly beat in 1 cup sugar, then 2 teaspoons lemon rind; continue to beat until very stiff and glossy, about 10 minutes. Spoon meringue into well buttered pie plate, and spread evenly to form a shell. Bake at 300 degrees F (150 degrees C) for 50 minutes, until firm. Cool.
Beat egg yolks, slowly adding remaining 1 cup sugar, beat until thick. Mix cornstarch with lemon juice, and add to yolk mixture. Stir in water and 2 teaspoons lemon rind. Cook over low heat until thick and bubbling. Remove and chill, covering with plastic wrap to keep film from forming on surface.
Beat whipping cream, and fold into cold lemon custard. Spoon into meringue shell. Cover, and chill 3 to 4 hours before serving.
