For the Custard: Combine whole eggs, yolks, sugar, salt, and lemon zest in a 3-quart stainless steel saucepan, then whisk in lemon juice. Cook over low heat, stirring constantly but not vigorously, until warm to the touch, about 3 minutes. Increase heat to medium-low and continue cooking and stirring until thick and steaming-hot (custard should register 170°F on an instant-read thermometer), about 8 minutes. Immediately strain into the prepared crust, smooth into an even layer, and cover with aluminum foil. Bake until smooth and firm, about 10 minutes. Remove foil and cool to room temperature, then re-cover and refrigerate until cold and firm, about 1 hour.