Cut lemons into quarters. Soak them in 20% brine solution for two to three months. De-brine in fresh water. Take sugar and three fourth cup of water in a pan and heat. Add citric acid and cook till it reaches 78° brix or a sugar syrup of one string consistency. Add debrined lemons. Mix and cook for three to four minutes.
Remove from heat and add salt, coriander seeds, cumin seeds, fennel seeds, asafoetida and mix. Add black salt and mix. Cool and add red chilli powder and mix. Transfer into sterilized bottles and store.