Light, refreshing, and pretty to look at.
Mix together the gelatin, ½ cup sugar and the salt in the top of the double boiler. Beat the egg yolks with the water, lemon and lime juices; stir into the gelatin mixture. Place over boiling water and cook, stirring constantly, until the gelatin dissolves and the mixture thickens slightly (about 6 minutes). Add both rinds. Chill, stirring occasionally, until the mixture mounds slightly when dropped from a spoon.
Beat the egg whites with the cream of tartar until stiff but not dry; then gradually add the remaining ¾ cup sugar and beat until very stiff. Fold in the gelatin mixture. If necessary, chill until the mixture will pile. Turn into the pie shell, piling high in center. Chill until firm.