The Preparation
In a heatproof bowl or heavy saucepan, whisk together the eggs and sugar until combined.
Add the lemon juice and lemon zest. Whisk to combine.
Cook over medium heat, stirring or whisking constantly, for about 10 minutes until the mixture thickens enough to coat the back of a spoon.
Remove from heat. Add the butter pieces one at a time, whisking each in until melted and incorporated.
Strain through a fine mesh sieve for a smooth curd.
Pour into jars or a bowl. Place plastic wrap directly on the surface to prevent a skin from forming.
Refrigerate until cooled and set, at least 2 hours. Keeps in the refrigerator for up to 2 weeks.
