Serve this richly-flavored curd with scones or pound cake, or whip it into our Lemon Mousse.
In a medium saucepan, whisk eggs, sugar, and zest to combine. Whisk in lemon juice; add butter.
Cook lemon mixture over medium heat, stirring constantly, until thickened, 7 to 9 minutes. Immediately pour through a fine-mesh sieve into a bowl. Press plastic wrap directly on surface of curd, and refrigerate until cool, at least 2 hours and up to 3 days.