1 c. sugar
2/3 c. lemon juice
1 tsp. grated lemon rind
2 tbsp. cornstarch
3 egg yolks
1 egg
2 tbsp. butter

Mix sugar and cornstarch. Add lemon juice, grated rind, and butter. Cook slowly over low heat, stirring constantly. Beat eggs until foamy and add to warm lemon mixture. Continue stirring over low heat until mixture thickens.