Soak the tamarind in ½ cup of warm water.
Rinse the rice well and add it to the Instant Pot.
Squeeze the pulp out of the tamarind and strain it out. Repeat the process with another ½ cup of warm water. You dont have to soak it this time as the tamarind is already broken down. This is just to get any extra pulp in the tamarind.
Add the tamarind pulp, rasam powder or sambar powder, jaggery, chopped tomatoes, turmeric powder, black pepper, salt and water to the rice.
Close the Instant Pot and set the knob on the lid to SEALING.
Set the Instant Pot to MANUAL mode and adjust time to 7 minutes.
Once done, wait for pressure to release naturally, move the knob to VENT and open carefully once all the pressure is gone. If you are in a hurry, you can do a quick release by moving the knob to VENT position manually and then open once pressure is completely gone. You can tell when the little pin next to it goes down.
Heat the ghee or oil in a small saucepan and add the mustard seeds to it. Once they splutter, add the asafetida and curry leaves. Pour this on top of the rasam rice and mix well.
Garnish with minced cilantro and serve hot.