1/2 cup (1 sticunsalted butter, cut into pieces

In a heatproof bowl, whisk together the eggs, sugar, lemon juice and salt until blended. Add the butter and lemon zest. Set the bowl over (not ia saucepan of simmering water and cook, whisking constantly, until the mixture has thickened to the consistency of mayonnaise, 12 to 15 minutes.

Pour the mixture through a fine-mesh sieve into a medium bowl. Place a piece plastic wrap on the surface of the lemon curd to keep a skin from forming. Refrigerate until completely cool, at least 2 hours and use with in a week.