Put the bitter gourds in a large bowl, season with salt, and add the turmeric and tamarind extract. Mix together and soak for 5 minutes. Squeeze the bitter gourds well and drain out any excess liquid, then soak in a large bowl of fresh water for 10 minutes. Squeeze out the water again and place the bitter gourds on a plate.
Put the gram flour, chilli powder, garlic paste, and coconut in a bowl. Season with salt and mix together.
Heat the oil in a large, heavy-based frying pan (skillet) over medium heat and lightly fry the bitter gourds for about 2 minutes. Remove from the pan with a slotted spoon and set aside.
Add the onions to the pan and fry for about 5 minutes, or until light brown. Add the fried bitter gourds and fry for 2 minutes.
Add the coconut and garlic spice mixture and stir-fry for a further 2 minutes, then add the jaggery or sugar and cook for 3-4 minutes.