In one mixing bowl, beat the egg yolks with the stand mixer or electric hand mixer on high speed for 5 minutes or until thick and light yellow in color. Add the lemon zest, lemon juice and water and beat on low speed until combined. Gradually beat in 1 cup of sugar on low speed and continue to beat on low speed for 5 minutes until the egg yolk mixture has thickened and doubled in volume. Add the flour 1/4 cup at a time and using a spatula, gently fold the flour into the egg yolk mixture.