Mix gelatin, 1/2 cup sugar, salt, water and lime juice.
Beat in egg yolks
Heat over medium heat until the gelatin is dissolved.
Remove from heat and add lime rind.
Cool until the mixture begins to thicken.
Beat egg whites until they begin to form soft peaks. Gradually add 1/2 cup sugar and continue to beat until stiff.
Fold the egg whites into the gelatin mixture.
Spoon into the pie crust. Chill until firm.
Whip cream with vanilla sugar. Spread on pie.
