Step 1

In a small saucepan, combine sugar, lemon juice, lemon zest, and eggs.

Step 2

Add the butter and cook over low heat, stirring continuously with a whisk, until the first bubble appears on the surface of the mixture and the curd is thick enough to hold marks of the whisk, about 6-8 minutes.

Step 3

Strain the lemon curd through a fine-mesh strainer if you don't want the lemon zest in the curd. Transfer the hot lemon curd to a bowl or jar and cover the surface with plastic wrap. Refrigerate until cold, then take off the plastic wrap and replace with a lid.

Step 4

The curd keeps fresh in the refrigerator for about 1 week.