Now add ridge gourd pieces, toor dal, onions, tomatoes, green chillies, and tamarind (clean and wash) and turmeric powder in a cooking vessel and cook till the dal becomes tender. (If you want you can do this in a pressure cooker also. 2 to 3 whistles are enough)
Switch off the stove.
Then mash the cooked items and keep aside.
Now take a separate pan and heat with 4 tsp of oil.
Add mustard seeds, cumin seeds, curry leaves and asafoetida.
When they start to crackle adds the cooked and mashed dal and adjusts the salt.
