Combine sugar and cornstarch in saucepan; gradually add water, blending until smooth. Cook over medium heat, stirring constantly till mixture becomes thick and clear; remove from heat. Stir small amount of hot mixture into egg yolks; add to hot mixture in saucepan and cook 2 minutes. Add lemon juice, peel and butter, blend well. Serve, warm or cold. Makes 2 3/4 cups