Use this recipe to make our Lemon-Blueberry Tart.
Strain the yolks and whole eggs and lemon juice through a sieve into a medium-heavy non-reactive saucepan. Add sugar; whisk to combine.
Cook over low heat, stirring constantly with a wooden spoon, until the mixture thickens and coats the back of the spoon, about 15 minutes. Remove from heat; stir in the butter, one piece at a time, until fully incorporated. Stir in lemon zest. Place over a bowl of ice to bring to room temperature.