Take tur dal wash it and soak it in water for 1/2 hour.
Slit the green chilies into halves. cut the tomatoes into small pieces.
After the whistle comes set the flame to low and cook for seven to ten minutes.
Then take a pan add oil add the tempering(mustard, Fenugreek, urad, channa and cumin seeds) after it crackles add curry leaves onion finely chopped and fry till translucent add the chilies and tomato pieces, Sambar powder and fry for 5 minutes then switch off.
Now open the cooker lid after the pressure has escaped and grind the dal to a smooth paste with a dal ladle or mixie.
Add the copped coriander. taste if you want you can add some more salt. Now close the lid and cook for one whistle.