Set the toor dal to boil in 3/4 litre of water in a large pan or eeya chombu
Break open the vilampazham fruits with a stone. Reserve the shells. The pulp and fibres come out easily but now the pulp needs to be extracted.
Put it in a bowl, add a little water and mash with your hands to loosen the fibres and seeds
Strain this and reserve the extracted pulp. Repeat by adding more water a few times until all the pulp has been extracted.
Taste a little of this vilampazham water—if it’s very sour, you’ll need to add no tamarind. If not, tamarind may be needed to bring the rasam together.
Once the dal is cooked, pour the vilampazham water in
Add the turmeric, rasam powder, jaggery, and salt
If you need to add tamarind water, do so now as well.
Drop a few of the vilampazham shells into the rasam, too.
Leave this to simmer until the raw smell of tamarind is gone (if using) or until the mixture looks like it will soon froth