I just love using preserved lemons to add an intense bit of lemon tartness to dishes, savory or sweet. In many recipes where I call for these, you can substitute lemon zest, but it’s just not the same.
Just remember that when you are using lemon rinds, it’s important to remove all of the pith before using, as that’s where the lemon’s bitterness hides and your end result will overpower a dish very easily. Also, you want to cut the lemon peels as thinly as possible. They’re very intense and a little goes a long way!
Bring a large pot of water to a boil with ¼ cup of the salt. Boil 4 of the lemons whole until they begin to soften, 5 minutes. Remove them with tongs and set them aside to cool. Add the remaining 5 lemons to the boiling water for 5 minutes, and then remove them and set them aside to cool with the others.
In a small pot, combine the remaining 2 cups salt, sugar, vodka, fennel seeds, peppercorns, red pepper flakes, and mustard seeds. Set the pot over low heat and simmer until the sugar and salt have dissolved, about 15 minutes.
Meanwhile, cut the cooled lemons, running your knife lengthwise from just below the top of the lemon to just above the bottom tip, so as to cut it into quarters without cutting all the way through the fruit. Stuff the lemons into a large glass jar with a lid (at least ½-gallon sized). Pour the salt liquid over the lemons, pushing the fruit down to make sure it’s submerged. Let the liquid come to room temperature, and then close the lid tightly. Let the lemons sit at a cool room temperature for 2 weeks*, then they are ready to use. Once you open them, the preserved lemons can be refrigerated for up to 6 months.