Preheat oven to 400 F.

Using electric beater, beat yolks until light and lemon colored in small bowl of mixer Add sugar to yolks very gradually and beat until well blended.(5 to 7 minutes) Gradually add lemon juice, beating well. Pour mixture into top portion of double boiler.Cook over very hot, not boiling, water, whisking until thickened and foamy,(about 10 minutes).

Soften gelatin in cold water for 5 minutes, then stir into hot yolk mixture until dissolved. Now put yolk mixture back in small mixer bowl and put this into a bowl of ice water and whisk mixture until cooled(Remove when it shows signs of thickening) Add lemon peel.

In large bowl of mixer, beat whites until soft peaks form.Add cream of tarter. Gradually add sugar to egg whites and beat until stiff peaks form. Fold one-quarter of the white mixture into the lemon mixture and beat until smooth. Carefully fold into egg whites until well blended.

Pour into baked pie shell.Refrigerate.Top with whipped cream around perimeter, if desired.