1 Rinse the etrog. Cut it lengthwise and slice very thin. Remove any seeds. 2 Soak the fruit overnight in water, making sure to fully cover it. Place it in a pot and bring it to a boil. 3 Remove the etrog and change the water and bring to a boil again. Then remove the fruit and weigh it. Match with an equal amount of sugar (no need for any water). 4 Cook over low flame for about 45 minutes or until it takes on a jam-like appearance.