Select sauté on the instant pot and adjust to normal.
Add oil to the pot.
When the oil is hot, add mustard seeds, whole dried red chili peppers, curry leaves, and asafeotida.
When the mustard seeds crackle, add the onions, and stir. Keep stirring occasionally.
When the onions turn golden in roughly for 2 to 4 minutes add the ginger garlic paste.
Add the chopped tomatoes and serrano pepper, and sauté for a few minutes until the tomatoes get mushy for 2 minutes. Keep stirring.
Then add ground turmeric, salt, red chili powder, coriander powder, chettinad masala powder, and water. Stir well.
Add the shrimp and stir. Make sure nothing is stuck to the bottom of the pot and scrape the bottom of the pot well.
Press cancel.
Secure the lid on the pot and close the pressure-release valve.
Select manual and cook at high pressure for 1 minute.
When cooking is complete, use quick pressure release to depressurize.
Open the lid.
Select sauté and add the tamarind concentrate. Stir for 30 seconds.
Press cancel.
Transfer in a serving bowl immediately.