In a small saucepan, mix together sugar and cornstarch thoroughly. Stir in cold water until cornstarch is dissolved. Add boiling water and cook over medium heat, stirring constantly until thickened and clear in color.
Remove from heat and stir in butter, lemon extract, and lemon juice; set aside until ready to serve.
Makes approximately 1 cup lemon sauce.
Lemon Sauce Recipe: https://whatscookingamerica.net/sauces_condiments/lemonsauce.htm