Stir together sugar, chopped butter, grated lemon rind, and juice in a large saucepan over medium heat and cook, stirring constantly, until sugar dissolves and butter melts.
Whisk about one-fourth of hot sugar mixture gradually into eggs; add egg mixture to remaining hot sugar mixture, whisking constantly.
Cook over medium-low heat, stirring constantly, 15 minutes or until the mixture thickens and coats a spoon. Remove from heat; cool. Cover and chill up to 2 weeks.