In a 2-quart microwave container, stir together sugar and cornstarch. Gradually stir in milk
until smooth. Stir in egg yolks, rind, and juice. Add margarine. Mix and cook at 70% power
until boiling (about 2-4 minutes), stirring once. Boil for 30 seconds to 1 minute. Remove and
cover mixture with plastic wrap; refrigerate 45 minutes to cool, but do not set. Fold in sour
cream and turn into the crust. Refrigerate at least 2 hours or until set. Garnish with whipped
cream.