If using fresh tamarind, soak it in 1/2 cup of hot water for about 10 minutes while you prep the remaining ingredients. Strain to obtain the juice and discard the tamarind flesh. If using tamarind paste, skip this step.
Add dal, tomatoes, tamarind juice (from step 1) or paste, turmeric powder, rasam powder, green chilies, chili powder, jaggery and salt along with 4 cups of water in the steel insert of the Instant Pot. Mix well.
Select “Pressure Cook.” Adjust the time to 12 minutes and set the pressure selection to high. Cover the Instant Pot lid and lock it. Make sure the vent is at sealing position.
Once the cooking cycle is complete, wait for 10 minutes before releasing pressure.
If using a stovetop pressure cooker, follow the same steps as listed for Instant Pot. Cook on medium-high heat and wait for the vent/whistle to go off 3-4 times. Take it off heat and let the cooker cool down before you open the cover.
Tempering process
Add oil or ghee to the tadka pan kept over medium-heat.
When the oil is hot, add mustard seeds and asafoetida. Once the mustard seeds start to sputter, add urad dal, garlic cloves and a sprig of curry leaves.
Let them sizzle for about 10 seconds and then pour this mixture over the rasam.
Garnish with cilantro and mix well.
Notes
If using fresh tamarind, take chunks of tamarind from the package and roll into a ball. The ball should be approximately the size of a ping pong/golf ball (approximately 1.5 inches in diameter). Soak it in 1/2 cup hot water for about 10 minutes before use. You can also substitute fresh tamarind with 1/2 tablespoon tamarind paste or a tablespoon of lime juice.