Cut the tomatoes into large pieces and blend in the mixer. This way, the skin is not visible but adds body to the rasam.
Add 3 cups (750 ml) of water, cumin powder, pepper powder, turmeric powder, salt and chilli powder (optional) to the pureed tomatoes and boil for about 2 minutes.
Heat oil or ghee. Add the remaining spices, curry leaves and garlic (optional).Turn off heat as soon as the spices pop and aroma of the crushed garlic is released. Add the dried chillies last.
Add the hot oil and spices to the liquid tomato broth together with the sprig of fresh coriander leaf.