In double boiler, soften gelatin in water. Add egg yolks and salt. Cook over simmering water while stirring constantly until gelatin dissolves and mixture is slightly thick (about 5 minutes).
Remove from heat and add in lemonade concentrate. Chill until mixture mounds when spooned.
Beat egg whites until soft peaks form; gradually add in sugar, beating until stiff peaks form. Fold into gelatin mixture. Fold half of the whipped cream into gelatin mixture.
Pile into cooled baked 9- inch pie shell and chill until firm. Serve with remaining whipped cream.