In a pan, roast cumin seeds, peppercorns, toor dal and red chilly until nice aroma comes. Cool and grind to a fine powder.
Soak tamarind in 1 cup warm water and extract the juice. Add 1 cup water to this tamarind extract.
In a vessel, add the tamarind juice, cumin-pepper powder, turmeric powder, asafoetida, salt and mix well. Bring to boil.
Boil well till raw smell of tamarind goes. Simmer until the rasam turns frothy. Remove from heat.
In a pan, heat ghee and add mustard seeds. When in splutters, add cumin seeds, curry leaves and pour over the rasam.