Soak the tamarind in little water in a small bowl for sometime and extract the juice out of it.
Add the dal, bottle gourd, water, salt to taste in a pressure cooker and pressure cook for about 3 whistles. Let the pressure release by itself and coarsely mash the dal and bottle gourd with the back If the laddle.
Heat oil in a pan. Add the mustard seeds, cumin seeds and red chillies a let it crackle.
Add the curry leaves, green chillies, ginger, garlic and saute for about 2 mins.
Add the turmeric powder and asafoetida and tamarind juice and cook for a min or two.
Add this tempering to the dal bottle gourd mixture, give a good stir and take off the heat.