Bring a saucepan of water to a gentle simmer and set a glass or metal bowl over the top to create a double boiler. In the bowl, whisk together eggs, yolks, sugar, butter, lime zest, and lime juice.
Cook over the simmering water, stirring frequently, until very thick, about 20 to 25 minutes (the curd must reach 170 degrees on a thermometer to thicken). Strain through a fine-mesh strainer or cheesecloth, then cover and chill completely.
Notes
Limes: Always zest your limes before you cut them open to juice. It’s much harder to zest half of a lime!
Yield: This recipe makes 2 1/2 cups of lime curd.
Storage: Store lime curd covered in the refrigerator for up to 1 week.