The curd is done when it is thick enough to coat the back of the spoon and to hold a clear trail when you run your finger through it. When stirring, the spoon should leave a clean trail in the curd.
- 4 large eggs, plus 4 large egg yolks
- 1 1/3 cups sugar
- 2/3 cup fresh lemon juice (about 4 lemons)
- 10 tablespoons unsalted butter, cut into pieces
- Press-In Crust
In a small saucepan (off heat), whisk together eggs, egg yolks, sugar, lemon juice, and a pinch of salt until smooth; add butter.
Place pan over medium heat. Cook, stirring constantly with a wooden spoon or heatproof flexible spatula, until lemon curd is thickened to the consistency of a loose pudding, about 8 to 10 minutes.
Pour curd through a fine-mesh sieve into cooled crust. Cool to room temperature. Refrigerate tart until filling is firm, 2 to 3 hours. Unmold before serving.