Wash and drain the dal and soak it for 10-15 minutes in water.
Cook into pressure cooker with 4 cups of water, salt and turmeric powder till to 3-4 whistles.
Add mooli in cooker and again cook in pressure cooker for 2-3 whistles or till to tender. Remove from the cook and mix well.
Heat the oil in a pan, add mustard seeds, red chilies, curry leaves and saute few seconds.
When they start crackle, add onion and saute them till to translucent.
Add chopped tomatoes and cook till to mashy.
Add sambhar masala, tamarind puree and mix well.
Add this tempering into dal mixture and cook for again five minutes.
Now mooli sambhar is ready to serve with rice or idli.