Bring a medium pot of water to a boil. Reduce heat to medium-high. Whisk lemon juice, sugar, and eggs, in a medium heatproof bowl; place over pot of simmering water and cook, whisking constantly, until mixture has thickened, 5–6 minutes. Remove mixture from heat and transfer to a blender. With blender running, slowly add butter, 1 piece at a time; blend until butter is completely incorporated.
Transfer lemon curd to a small bowl and place a piece of plastic wrap directly on the surface of the curd. Chill for at least 3 hours before serving. Do ahead: Lemon curd can be made 3 days ahead. Keep chilled.
Editor’s note: This recipe was originally published in May 2012. Head this way for our favorite lemon bars, an extra-lemony pound cake, the ultimate lemon meringue pie, and more favorite lemon desserts →
