My favorite lemon curd, from Allrecipes.com

• 3 eggs
• 1 cup sugar
• 1/2 cup fresh lemon juice
• 1/4 cup butter or margarine, melted
• 1 tablespoon grated lemon zest

Directions

1. In the top of a double boiler, beat eggs and sugar. Stir in lemon juice, butter and lemon zest. Cook over simmering water for 15 minutes or until thickened.

My note:  Remove from heat immediately and continue stirring so not to curdle your curd.