3/4 c. sugar
3 tbsp. cornstarch
1/4 tsp. salt
3/4 c. water
1 tsp. grated lemon peel
1 tbsp. butter
1/3 c. lemon juice
4 drops yellow food color (optional)

Mix sugar, cornstarch, and salt in a saucepan. Stir in water gradually. Cook, stirring constantly, until mixture thickens and boils. Boil and stir 5 minutes. Remove from heat; add lemon peel and butter. Stir in lemon juice and food color; cool. If filling is too soft, refrigerate until set.