Wash nicely and coarsely peel Karela.
Cut into medium thin roundels.
Sprinkle salt on the cut pieces and keep in sun(preferred) for at least 1 hr. After that squeeze water from it. you can rinse karela pieces in water if you want.
Thinly slice the onions. If using green chillies, either chop finely or slit in half.
In a pan or kadhai, add mustard oil. Heat oil till it's smoking point. Switch off the gas for a minute, cool the oil a for a minute and then add cumin seeds and asafoetida.
When the seeds crackle, add sliced onions and saute for a minute.
Add all the dry spice powders except dry mango, add sliced karela pieces and with salt and mix everything. Add 1-2 tbsp of water if required, cover the pan and cook the vegetable for 5-6 minutes.
Keep stirring the vegetable in between while it cooks so that it doesn't stick to pan and burns.
Check the vegetable once done, add dry mango powder and jaggery powder or honey(optional).
Serve with chapatis/dal chawal/kadhi chawal or khichdi.