Start the pressure cooker in sauté mode (high flame for stovetop pressure cooker) and heat 2 tbsp butter/oil in it. Add onions and sauté for 3 minutes.
Add bell pepper and sauté for another 2 minutes. Add tomatoes, pav bhaji masala and salt. Add the ground chili paste. If anything is stuck to the bottom of the pot, scrape it with a spatula.
Add cauliflower, potatoes, carrots, and green peas. Mix well.
Press cancel and close lid with vent in sealing position. Change the setting to manual or pressure cook mode at high pressure for 8 minutes. When the instant pot beeps, release the pressure naturally.
Open the pressure cooker and use an immersion blender to coarsely grind the ingredients. You can also use a potato masher to mash the bhaji to the desired consistency.
Change to sauté mode and let the bhaji boil for a minute. Mix in the lime juice. Bhaji is ready to be served.