Ingredients

1/2 cup sugar 

2 large eggs 

2 teaspoons grated key-lime zest plus 1/4 cup freshly squeezed key-lime juice (6 limes) 

4 tablespoons unsalted butter, cut into small pieces 

Preparation

Combine sugar, eggs, lime zest, and juice in a medium nonreactive saucepan, and set over medium-low heat. Cook, whisking constantly, until mixture begins to thicken and holds the mark of the whisk, 10 to 12 minutes.

Remove pan from heat, and whisk in butter, a piece at a time, until well combined. Strain mixture through a sieve into a glass bowl. Lay plastic directly on surface to prevent a skin from forming. Chill 3 hours or overnight to set the curd.