Rinse the rice very well, transfer the rinsed rice to the inner pot of instant pot (discard the water used for rinsing the rice).
Add enough water (as the amount mentioned in recipe card, here 4 cups of water for 2 cups of ponni rice) and mix well, make sure there is water at the bottom of the pot.
Close the instant pot with lid in sealing position, press the 'rice' button and cook for 10 minutes (if it's not set for 10 minutes, adjust the time to 10 minutes). In many models, you can't adjust the time for rice button and if it's automatically set for 12 minutes instead of 10 minutes, you can use that too.
Once the cooking is done and the pot beeps, press the 'keep warm/cancel' button and wait for a natural pressure release of 10 to 12 minutes (if the rice button was set for 12 minutes cooking, you may just go for 10 minutes natural pressure release).
After a natural pressure release of 10 to 12 minutes, carefully do a manual release by turning the lid to venting position slowly, releasing the pressure manually very carefully and gradually.
Once the pressure is all released, carefully open the instant pot and fluff the rice with a fork or use a spoon or spatula and gently mix the rice.