For filling, in a small bowl, sprinkle gelatin over cold water and set aside. In a heavy, medium saucepan, whisk together egg yolks, the 1 cup sugar, the lemon peel, lemon juice, and salt. Cook and stir over medium heat until mixture is slightly thickened and bubbly. (Mixture may look curdled at first, but it becomes smooth as it cooks.) Remove from the heat. Stir in the gelatin until dissolved. Cover and cool to room temperature.
In a large mixing bowl, combine the warm water and dried egg whites, stirring until egg whites are nearly dissolved. Beat with electric mixer until soft peaks form (tips curl).
Gradually add the 3/4 cup sugar, beating until stiff peaks form. Fold cooled egg yolk mixture into beaten egg whites. Chill until mixture mounds, gently stirring occasionally. Pile into the baked pie shell. Cover and chill for at least 4 hours.
Serve with whipped cream, if you like. Makes 8 servings.
Look for the dried egg whites where baking supplies are sold, such as craft stores or supermarkets.
Stir together flour and salt. Using a pastry blender, cut in shortening until pieces are pea-size. Sprinkle 1 tablespoon of the water over part of the mixture; gently toss with a fork. Push moistened dough to the side of the bowl. Repeat moistening dough, using 1 tablespoon of the water at a time, until all the dough is moistened. Form dough into a ball. On a lightly floured surface, use your hands to slightly flatten dough. Roll dough from center to edge into a circle about 12 inches in diameter. To transfer pastry, wrap it around the rolling pin. Unroll pastry into a 9-inch pie plate. Ease pastry into pie plate, being careful not to stretch pastry. Trim pastry to 1/2 inch beyond edge of pie plate. Fold under extra pastry. Crimp edge as desired. Generously prick bottom and side of pastry in pie plate with a fork. Prick all around where bottom and side meet. Line pastry with a double thickness of foil. Bake in a 450 degree F oven for 8 minutes. Remove foil. Bake 5 to 6 minutes more or until golden. Cool on a wire rack.