There’s a Yiddish expression to describe something that has no value: “an etrog after Sukkot.” Considering that an etrog can cost $30 or more before Sukkot—the holiday in which this citrus fruit is ritually important—and yet seems to be worth nothing once the holiday ends, it’s an apt expression.
So, what can you do with an etrog after Sukkot? It would be wasteful as well as disrespectful to simply toss this exotic fruit in the garbage—especially when there are, in fact, many uses for it.
Wash each etrog in cold water and cut into quarters. Remove the seeds. Grate the fruit, including the peel and the white membrane, on the largest holes of a box grater.
Place the grated etrog in a bowl and cover with cold water. Let sit for two days, draining and adding fresh cold water twice a day. Drain and squeeze the fruit to extract as much liquid as possible. In a large heavy saucepan, stir together the sugar and water. Add the etrog mixture, bring to a boil over medium heat, and cook, stirring, until most of the syrup has been absorbed and the fruit is translucent.
Pack the preserves into sterilized jars, filling them to 1/4 inch from the top. Wipe off the rims, screw on the lids, and turn the jars upside down on a dishtowel. Leave them undisturbed for 12 hours, after which they should be vacuum-sealed and can be stored in the cupboard. If any don’t seal, just refrigerate them for up to three months.