Tender lentils slow-simmered with warming turmeric, finished with a sizzling tarka of golden ghee, roasted cumin, and fresh coriander.
Soak the tamarind in 1 1/2 cups warm water, mash well, and strain the pulp into a pot.
Coarsely crush the peppercorns, cumin seeds, and garlic.
Add the tomatoes, crushed spices, and salt to the tamarind water and simmer until the tomatoes collapse and the raw smell fades.
Heat the ghee, pop the mustard seeds, and add the curry leaves until fragrant.
Pour the tempering into the rasam, cover for 5 minutes, and serve hot with rice or as a soup.