Put the rinsed toor dal, turmeric and one cup of water in a pressure cooker and cook for 3 whistles.
Wash and pressure cook the tamarind with water for 3 whistles. Drain the water and let them cool.
Peel the cooked tamarind and discard the peel.
Add water to the peeled tamarind. Squeeze the pulp and extract the juice. Keep it aside.
Heat oil in a pan. Add the mustard seeds, chana dal, urad dal and cumin seeds and let them splutter.
Add the chopped green chillies, red chilli, curry leaves and hing and fry for a minute.
Then add the chopped onion and fry until light golden brown color.
Add the cooked dal, tamarind juice, salt and red chilli powder to it and let it boil for a couple of minutes.
Turn off the flame and serve hot with rice or roti.