Lemon Curd

Directions

1. 1
   Whisk together lemon juice, lemon zest, sugar, and eggs in a 2-quart saucepan.
2. 2
   Cut butter into bits and add to mixture.
3. 3
   Cook mixture, stirring constantly, over moderately low heat until curd is thick enough to hold marks of whisk and first bubble appears on surface, about 6 minutes.
4. 4
   (You can make the curd 1 week ahead and chill it, covering its surface with plastic wrap.)