Wash the dal thoroughly and soak for 20 minutes. Add castor oil, turmeric powder and water. Add garlic cloves and chopped tomatoes. Cook in medium flame for 6 whistles. Let the pressure release on its own.
Carefully take the dal water along with cooked tomatoes into a separate vessel. This dal water is used to make paruppu rasam.
In a spice jar take garlic , cumin and pepper corns.
Grind into a coarse paste.
Heat oil in a pan. Add mustard seeds. Once the mustard seeds crackle add the ground spices.
Then add curry leaves, red and green chillies.
Now add asafoetida and saute everything together.
Next add dal water, salt, tamarind water and coriander leaves.
Bring the mixture to a boil. Once the mixture starts to boil, switch off immediately.
Serve with hot steamed rice or as such as a soup.