Prepare the lentils by soaking them for 30 minutes. Cook the lentils with the water using a pressure cooker or boil them in hot water.
Heat a pot, add sesame oil, and season the mustard seeds. After they splutter, sprinkle the hing or asafetida into the oil and toss in the dried red chilis and curry leaves.
Purée the lentils using a hand blender. Add the puréed lentils with the water. Mix in the turmeric powder, salt, and crushed garlic.
Add the puréed tomatoes. Powder the three peppercorns and cumin seeds in a coffee grinder or mixie and add to the rasam.
Bring to a boil, and then turn off the heat. Add the both the lime and lemon juices. Garnish with chopped cilantro.
Notes
Notes:
Do not add the lemon juice while the rasam is boiling. Turn off the heat and then add the lemon and lime juices.
Pulse the lentils well so that they are not grainy. What you want is a smooth soup that is easy to consume and digest.