The etrog (citron) is used by Jews worldwide for the holiday of Sukkot. What do you do with it after the holiday? My instructions are for someone like me who (almost) never makes jelly. You need 2 days before cooking to soak the etrog to get rid of bitterness. Get long tongs to take jars out of boiling water. For a small quantity, use 2 esrogim, 3/4 cup sugar, 1 tblsp pectin, 3-4 tblsp orange marmalade. Save & re-use glass jars with lids (jelly, pickles, anything).