Soak tamarind in 2 cup of hot water for 10 minutes. Remove the seeds and keep the water aside. Heat oil in a pan and add mustard seeds, urad dhal, onions, garlic, tomatoes and asafetida and fry for 5 minutes. Then add the egg plant and fry until tender. Pour the tamarind extract and add turmeric, red chili powder and salt. Close the pan. Turn the heat to medium and let it boil until it becomes a thick gravy. Garnish with chopped coriander leaves.