Start the instant pot in sauté mode and heat oil in it. Add all the tempering ingredients.
When the mustard seeds start to splutter, add the chopped onions and sauté for 2 minutes.
Add the chopped tomatoes, sambar powder and salt. Sauté for another 2 minutes.
Add all the vegetables, toor dal and water to the instant pot. Change the instant pot setting to manual or pressure cook mode for 8 minutes at high pressure with vent in sealing position.
When the instant pot beeps, let the pressure release naturally. Stir in the tamarind paste. Stir the sambar so it is mixed well.