Microwave Lemon Curd

In a microwave-safe bowl, whisk together the sugar and eggs until smooth. Stir in lemon juice, lemon zest and butter. Cook in the microwave for one minute intervals, stirring after each minute until the mixture is thick enough to coat the back of a metal spoon. Remove from the microwave, and pour into small sterile jars. Store for up to three weeks in the refrigerator.