Get nice long shaped Bitter gourds from the market. Wash bitter gourds twice with clean water then place them in a strainer or plate to drain out remaining water. Cut off its stems. Cut the bitter gourds into thin round pieces.
Put 1 tsp salt to the pieces of bitter gourds and keep aside for 1 hour in a utensil. This releases the bitter water from them, put these salt coated bitter gourds in boiling water and cover for 5 minutes. Keep the bitter gourd pieces in a strainer and remove excess water, keep the pieces on a washed cloth for 2-3 hours in the open/sun to dry the water on them.
Roast Heeng, Jeera, Methi and Saunff till they turn light brown. Grind these reoasted spices with yellow mustard to a coarse powder.
Now keep the bitter gourd pieces in a dry utensil, also put the roasted spices and salt, mix all these ingredients properly. Squeeze the juice from the lemons on the bitter gourd pieces and mix with a spoon.
Fill a glass or plastic container with the bitter gourds mixed in spices, you can also keep this container in the sun. Stir the pickle everyday for the next 4 days with a clean and dry spoon. Sour bitter gourd pickle with a mouth watering smell is ready. Serve during breakfast or dinner with hot paranthas.
This pickle can be eaten for 15-20 days. To increase its shelf life keep the pickle in the fridge or add mustard oil enough to submerge the pickle completely.