Heat oil in a pan, splutter mustard seeds and add dried red chillies.
Then add chopped onion and sliced green chilly. Sauté for 1-2 minutes.
Add tomato and curry leaves. Sauté for another 1-2 minutes.
Now add sambar powder, asafoetida, turmeric powder, red chilly powder and salt as required. Sauté for 1 minute to get rid off the raw smell.
Add hot water and cook it for 2-3 minutes.
Add tamarind water and cook for another 1 minute.
Mean time mix the gram flour in 1/4 cup water.
Finally add it into the curry and keep stirring.
Add curry leaves, coriander leaves and turn off the flame.
Super tasty Bombay Sambar is ready now.