Lemon Cake Filling - cooking recipe

Ingredients

1 cup sugar
4 tablespoons cornstarch
1 egg, beaten
1 cup water
1/2 cup lemon juice (fresh is best)
1 teaspoon lemon rind, grated (from the fresh lemon)
1 tablespoon butter (no substitutions)

Preparation

Mix sugar and cornstarch together thoroughly.
Combine the beaten egg, water, lemon juice and rind; add to dry ingredients.
Cook in a double boiler about 15 minutes, stirring constantly.
Add butter, beat well and cool before using.