Lemon Tart

1 cup sugar
1/4 cup cornstarch
1 cup milk
3 egg yolks, beaten
1/4 cup butter or margarine
1 tablespoon grated lemon peel
1/3 cup lemon juice
1 cup (8 ounces) sour cream
1 pastry shell (9 inches), baked
Whipped topping

In a saucepan, combine the sugar and cornstarch. gradually add milk until smooth. Cook and stir over medium-high heat until thickened. Reduce heat; cook and stir 2 minutes longer. Remove from the heat. Stir a small amount of hot liquid into egg yolks; return all to the pan. Bring to a gentle boil, stirring constantly. Cook 2 minutes longer (mixture will be very thick).

Remove from the heat; stir in butter and lemon peel. Gently stir in the lemon juice. Cover and cool completely. Fold in sour cream. Pour into pastry shell. Refrigerate for at least 2 hours before cutting. Garnish with whipped topping. Makes 6-8 servings.