Wash the bittergourd and cut them horizontally into two and then again vertically into two, remove the pith inside. slice them into roundels.
Once cut, sprinkle salt on them and let it rest for a minimum of 20 minutes. While the bittergourd is resting, let us prep the onions and tomatoes.
Chop onions and tomatoes fine. Once the bittergourd has rested for 20 minutes, strain it and give it a quick wash in running water and let it drain completely.
In a wide pan, Add oil, add the bittergourd in batches and shallow fry. i did it 2 batches, do not crowd the pan, you can also deep fry it, but i preferred to shallow fry.
Let the bittergourd, sizzle and shrink a bit and get a golden brown on them, once done, remove it with a slotted spoon and drain on a paper towel.
In the same pan, add mustard seeds, asafoetida and curry leaves, when the mustard splutter, add the chopped onions and saute until translucent.
Next add the tomatoes now to this add turmeric powder, salt and sambhar powder and mix well. Add 1/4 cup of water, cover and cook for 5 minutes, for the tomatoes to cook well and turn mushy.
Remove the cover and if the tomatoes are done, add the fried bittergourd to this and mix well.
Let it sit on the stove for another 3-5 minutes for the flavors to mingle. The consistency should be of a semi-gravy. You can also make this complete dry curry, just let it sit on the stove until the liquid is absorbed.
Take it off the stove, garnish with fresh coriander leaves and serve along with rice/roti.