1 vanilla bean, split
1 cup water
1/2 cup sugar
2 tablespoons cornstarch
1/8 teaspoon salt
1 tablespoon butter or margarine
2 tablespoons grated lemon rind
1/3 cup fresh lemon juice
Cook vanilla bean, water, sugar, cornstarch, and salt in a saucepan over medium heat, stirring until smooth and thickened.
Stir in butter and remaining ingredients, and cook until thoroughly heated. Remove vanilla bean.