Combine half of the butter, half of the sugar, lime juice and lime zest in a saucepan. Bring to a boil over medium heat, making sure to occasionally stir gently in order to dissolve the sugar.
Meanwhile, use a whisk to blend the eggs yolks and remaining sugar in a separate bowl.
Temper by gradually adding about one-third of the lime juice mixture, stirring the eggs and sugar constantly with a whisk. Next, remove the whisk from the egg mixture and begin whisking the lime juice mixture while you pour the tempered eggs and sugar into the saucepan. Place back over medium heat and continue cooking, stirring constantly with the whisk, until it comes to a boil.
Remove from the heat and stir in the remaining butter.
Strain the lime curd into a container and cover with plastic wrap placed directly onto the surface of the curd. Cool and store covered in the refrigerator for up to two weeks.