2/3 cup firmly packed light brown sugar
1 1/2 tablespoons butter, melted
2 teaspoons firmly packed lemon zest
2 tablespoons fresh lemon juice
1 egg, lightly beaten
Stir together brown sugar, melted butter, lemon zest, and lemon juice in a small saucepan. Stir in egg until blended. Cook over low heat, stirring constantly, 10 to 12 minutes or until mixture thickens slightly and begins to bubble around the edges. Use immediately.