Dissolve gelatin in boiling water. Stir in sugar till dissolved. Add lemon peel and juice; stir till combined. Cover; chill till mixture is the consistence of unbeaten egg whites.
In a medium mixing bowl, beat cream till soft peaks form. Fold into lemon mixture with Rosy Rhubarb Sauce. Chill till mixture mounds. Pile into piecrust. Cover and chill for 8 hours or till firm. Makes 10 to 12 servings.