Soak the lemon sized tamarind in 1 cup hot water
Roast the green chili on direct flame. I placed the chilis on a wire mesh.
You can insert it in a fork and roast it on direct flame one by one.
Roast till all the sides become charred.
In a pan add 1 tsp oil, ½ tsp cumin seeds, and 3 broken red chilies.
Once the cumin seeds crackle, switch off the flame.
Transfer the roasted green chili, and the cumin and red chili to a pan.
Add in few coriander leaves and curry leaves.
Add the chopped onions to this.
Mix well nicely with clean hands. Let this juice of the onions and the aroma of charred green chilis come out well.
Add 1 cup water to this.
Extract the tamarind extract and add it to the vessel.
Add 1 cup water.
Now add the salt as needed and mix well.
In a pan add 1 tsp oil and add ¼ tsp mustard seeds and curry leaves.
Once the mustard splutters, add it to the rasam.
Serve with hot rice and any poriyal or curry.