Pressure cook the toor dal with enough water until soft, then mash it well and keep aside.
Soak tamarind in water, extract the juice, and let it boil until the raw smell disappears.
Heat a teaspoon of ghee in a pan and add coriander seeds, channa dal, cumin seeds, and pepper.
Roast until golden brown, then add grated coconut and continue roasting until it turns light brown.
Allow this mixture to cool and grind it into a fine paste or powder.
In another pan, heat ghee and splutter mustard seeds.
Add curry leaves and dried red chilli, then sauté chopped tomatoes until they turn soft and mushy.
Add the tamarind extract to the pan along with turmeric powder, jaggery, salt, and rasam powder.
Let it boil well so the flavours combine. Once the tomatoes are cooked, add the ground masala and allow it to simmer.
When it starts to foam, add the mashed toor dal along with its water and mix well.
Finally, garnish with freshly chopped coriander leaves and switch off the flame.
Serve hot with rice or enjoy it as a comforting soup.