1In 1 1/2-quart saucepan, mix sugar, cornstarch and salt. Gradually stir in water. Cook and stir over medium heat until mixture thickens and boils. Boil and stir 1 minute longer; remove from heat.
2Stir in butter and lemon peel until butter is melted. Gradually stir in lemon juice and food color. Press plastic wrap on filling to prevent a tough layer from forming on top. Refrigerate about 2 hours or until set.
3Leftover filling can be tightly covered and refrigerated up to 5 days; do not freeze. Let stand 30 minutes at room temperature to soften; stir before using. Store cakes or pastries filled with Lemon Filling covered in refrigerator.