Bake a prepared pie shell.
In two small bowls, break and separate egg whites from yolks.
In a quarter of cup of water, soften one envelope of gelatin.
In a double boiler, combine 1/2 cup of sugar, 3 egg yolks and a pinch of salt. Stir constantly until thickened. Stir dissolved gelatin slowly into custard (hot egg mixture). Stir in grated lemon rind and fresh lime juice and allow to cool.
Beat the three egg whites, adding sugar gradually until soft peaks form. Fold egg whites gently into cooled custard, being careful not to deflate. Turn out into pie crust and spread smooth.
Chill at least 1 hour. Top with whipped cream, if desired.
