Pressure cook toor dal until very tender and set aside.
Heat ghee in a saucepan, add mustard seeds, cumin seeds, dry red chili, asafoetida and curry leaves, once the seeds start to splutter, add the tomatoes, tamarind paste, Mysore rasam powder, jaggery, turmeric and salt.
Simmer on low heat for 15~20 minutes till tomatoes are mushy.
Add the cooked dal and simmer for another 5 minutes for the flavors to blend.
Turn off the heat and stir in coconut milk and chopped cilantro. Serve with steamed rice.