Ingredients

1 cup sugar 

1 tablespoon finely grated lemon zest, plus 2/3 cup fresh lemon juice 

8 large egg yolks (egg whites reserved for another use) 

1/4 teaspoon coarse salt 

1 1/4 sticks unsalted butter (10 tablespoons), cut into 1/2-inch pieces 

Preparation

In a medium saucepan, off heat, whisk together sugar, zest, and egg yolks; whisk in lemon juice and salt.

Add butter and place pan over medium-high. Cook, whisking constantly, until butter has melted, mixture is thick enough to coat the back of a spoon, and small bubbles form around the edge of pan, about 5 minutes (do not boil).

Remove pan from heat while continuing to whisk. Pour curd through a fine-mesh sieve into a glass bowl. Press plastic wrap against the surface of curd and refrigerate until cool.