Turn Instant Pot to sauté(more) mode and heat oil. Add mustard seeds and allow them to crackle. This may take 2-3 minutes. Add asafetida, turmeric, jalapeños, green tomatoes, and salt.
Give a quick stir. Add brown sugar. Close Instant Pot with pressure valve set to sealing.
Pressure Cook (low pressure) for 5 minutes followed by quick release or natural pressure release.
Open Instant Pot and set to sauté mode. Mash the tomatoes using a masher, cook for 2 minutes stirring frequently. Garnish with chopped cilantro. Mix well and enjoy!