SOUR CREAM LEMON PIE

1 c. sugar
3 tbsp. cornstarch
1/4 c. butter
1 tbsp. grated lemon rind
1/4 c. lemon juice
3 unbeaten egg yolks
1 c. milk
1 c. sour cream
1 pie shell, baked

Combine sugar and cornstarch in a pan. Add the butter, lemon rind, lemon juice, egg yolks and milk. Cook over medium heat, stirring constantly until thick. Cool. Fold in the sour cream. Spoon the mixture into the baked pie shell. Top with meringue or whipped cream. Chill at least two hours before serving.