Sterilize a one-quart jar (with a tight-fitting lid) and the equipment you will be using: a cutting board, long-handled spoon, a large bowl, a small pan for toasting the spices, glass measuring cup, and measuring spoons.
Wash and dry the lemons or limes and cut off each end to remove the thickened rind. Then cut into 8 equal pieces, removing the center white pith, and deseed. Mix the lemon pieces, lemon juice, and salt together and place in the jar. Let sit for 30 minutes.
While the lemons are pondering their fate, measure out all the seeds you are using, and the carom (ajwain) seeds. (Do not toast the asafetida, Kashmiri chili, or nigella seeds.) In a small pan, add 1 tablespoon of oil and heat over medium-high heat. Add the seeds and just bring to a sizzle; about 1 minute. Cool and mix in the nigella seeds, if using, chili powder or flakes, asafetida (hing), and sugar.
Transfer the spices to the jar of lemons, add the oil, or enough to cover the lemons. Seal and shake to mix everything thoroughly. If you have a fermentation weight, that would come in useful to keep the citrus from popping above the surface of the oil.
Place in a cool dark place and give the jar a good shake once a day for a week. Open the jar and make sure that the oil is covering the lemons. If you need to, press the lemons under the surface of the oil. If you have a pickle weight, this is the time to use it. You can use the lemon pickle now, but I think it really comes into its own in the 3rd week. Store in the refrigerator after the 2nd week, up to 2 months.
Before serving, bring the pickle to room temperature before serving; about 10 minutes. Be sure to use a clean dry spoon to scoop out the pickle.
Water promotes spoilage so make sure your cutting board, lemons and the knife you are using are dry.
Feel free to substitute limes for lemons for this lemon pickle recipe.
Additional flavoring ideas:
1 tablespoon toasted fennel or anise seeds
sub out a tablespoon of salt with rock salt (sendha namak).
substitute 2 tablespoons of the oil with mustard oil
add 10 curry leaves and temper with the whole seeds
Any leftover oil is perfect for flavoring rice, salad dressings, and roasting vegetables.