Prep 10 m Cook 10 m Ready In 4 h 20 m
1 cup white sugar
1/3 cup lemon juice
1/4 cup butter
2 teaspoons lemon zest
Whisk eggs, sugar, and lemon juice in a double boiler over simmering water until mixed well, then continue to stir until thick, 7 to 10 minutes.
Drain through a mesh sieve to get rid of lumps. Fold in butter until well incorporated. Mix in lemon zest. Cover curd and chill in the refrigerator until it has thickened, about 4 hours.