Mix 1 cup sugar, the salt and gelatin in a medium saucepan. Blend egg yolks, water and lemon juice and stir into the sugar mixture. Cook over medium heat, stirring constantly, just until the mixture boils. Stir in lemon peel.

Place the pan in a bowl of ice and water or chill in refrigerator, stirring occasionally, until the mixture mounds slightly when dropped from a spoon. Beat egg whites and cream of tartar until foamy. Beat in 1 cup sugar, 1 tablespoon at a time, and continue beating until stiff and glossy. Do not underbeat. Fold in the lemon mixture. Pile into the pie shell and chill at least 3 hours or until set.