1 c. sugar
3 tbsp. cornstarch
1/2 tsp. salt
1 c. boiling water
2 tbsp. grated lemon rind
1/2 c. lemon juice
2 tbsp. butter

Combine all ingredients. Bring to a full, rolling boil, stirring constantly. Reduce heat, boil 1 minute, stirring. Let cool at room temperature. Beat with hand beater before using to fill white or yellow cake.

For orange filling, reduce boiling water to 3/4 cup substitute grated orange rind for lemon rind, 3/4 cup orange juice for lemon juice. Add 1 tablespoon lemon juice.