1 (9 inch) baked pie shell
2 c. sugar
3 tbsp. cornstarch
1/4 c. butter
1 tbsp. lemon rind
1/4 c. lemon juice
3 egg yolks
1 c. milk
1 c. sour cream
1 sm. Cool Whip

Combine sugar and cornstarch in a saucepan. Add butter, rind, juice, egg yolks and milk. Cook over medium heat until thick. Cool. Fold in sour cream. Spoon into pie shell. Chill 2 hours. Top with Cool Whip.