Soak the tamarind in 1 cup water for 30 minutes.
Meanwhile grind the unibic chilli butter cookies in a grinder.
Squeeze the pulp from the soaked tamarind with your hands in the water and keep aside.
Crush the tomatoes with your hands and add this to the tamarind pulp (you can also chop the tomatoes, if you prefer).
Make a coarse mixture in a dry grinder or in a mortar-pestle with the ingredients mentioned under rasam powder.
Heat oil in a pan and fry the mustard seeds and cumin seeds till they sizzle.
Add curry leaves and asafoetida and fry for some seconds.
Add the tamarind pulp - crushed tomatoes mixture.
Add the ground coarse rasam powder.
Stir and then add about 3 cups water and season with salt.
Bring to one boil and then simmer for 5-6 minutes, keep stirring occasionally.
Finally add chopped coriander leaves and give a stir.
Serve warm spicy, tangy, lip smacking rasam with rice papadam.
