In a medium-sized bowl, whisk the egg yolks and set aside.
In a medium-sized saucepan, whisk the water, sugar, cornstarch, salt, yuzu juice, lemon juice, and lemon zest together until it is a uniform mixture. Place the saucepan over medium heat. The mixture will be thin and cloudy at first, and then will begin thickening and bubbling after about 5 minutes. Once