Scrape the bitter gourds; make a slit on one side and remove the seeds. Rub the salt over and inside the karele and set aside for one hour. Wash under running water and set aside.
To prepare the stuffing, dry-roast the gram flour in a non-stick pan over low heat till fragrant. Remove from heat, transfer to a plate and set aside to cool. Add the onion, coriander leaves, salt, chilli powder, garam masala powder and carom seeds and mix well. Stuff the masala mixture into each karela and set aside.
Heat the oil in a kadai; add the onion and sauté till light golden brown. Add the ginger paste, and garlic paste and sauté for two minutes. Add the coriander powder, chilli powder, cumin powder and turmeric powder and mix well. Sauté the masala till fragrant. Add the stuffed karele, half a cup of water and salt. Cover and cook over high heat for three or four minutes. Lower heat and cook for ten to twelve minutes, stirring gently at regular intervals. Add the tamarind juice and mix well.
Cover once again and cook for another ten to fifteen minutes, till the bitter gourds are cooked.