Mix gelatin, 1/2 cup sugar and salt in saucepan. Beat egg yolks, lime juice and water together. Stir into gelatin mixture. Bring mixture to a boil on medium heat, stirring constantly. Remove from heat; add grated lime rind. Add a few drops of food coloring to tint mixture a pale green (optional). Chill in refrigerator for approximately 20 minutes until mixture coats a metal spoon.
Beat egg whites until soft peaks form. Gradually add 1/2 cup sugar and beat until stiff peaks form. Fold gelatin mixture into egg whites. Fold in 1 cup Whipped Cream. Place in pastry shell.
Chill until firm. Garnish with twisted lime slice. Serve with remaining Whipped Cream.
Combine cream, sugar and vanilla in a chilled medium mixing bowl. Beat on medium-high speed until soft peaks form. Can be refrigerated for up to 2 hours.
Prepare the Whipped Cream while the Gelatin Mixture chills in the refrigerator.