firstly, in a small blender take 1 tbsp cumin, 1 tsp pepper, 3 clove garlic and 2 tbsp coriander stem.
blend to a coarse paste without adding any water. keep aside.
in a large kadai, heat 2 tbsp oil and splutter 1 tsp mustard, 2 dried red chilli, few curry leaves and pinch hing.
add in the prepared masala paste and saute for a minute.
now add 1 tomato, ¼ tsp turmeric, 1 tsp salt and 1 chilli.
saute for a minute or until tomatoes turn soft and mushy.
further, add 1 cup tamarind extract and 3 cup water. mix well.
cover and boil for 8 minutes or until raw flavour disappears.
finally, add 2 tbsp coriander and enjoy south indian rasam with hot steamed rice.