Wash and pressure the cook the toor dal with enough water and ½ tsp turmeric powder, for 4-5 whistles.
Mash and keep aside.
Soak a small lemon sized tamarind in hot water for 10 minutes and extract 2 cups of tamarind water.
Finely chop the onions and coriander leaves.
In a pan add 3 tsp oil and add the mustard seeds.
Slit the green chili and break the red chili into half and add.
Saute for a minute and add the chopped onions.
I used small onions, you can use big onions too.
Saute till translucent.
Now add in the tamarind water.
Add ½ tsp turmeric powder and asafoetida.
Let this boil in medium flame for 7-8 minutes.
Once the raw smell of the tamarind goes off, add the cooked and mashed toor dal.
Add the chopped coriander leaves.
Add ½ cup of water to adjust the consistency.
Mix well and let this boil for 2-3 minutes.
Switch off the flame.
Kothamalli sambar is ready.
Serve with Pongal, dosai, or with rice too.