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.
Garnish with cilantro and sambar is ready to be served.
Stovetop Pressure Cooker Method
Follow the same steps as above in a stovetop pressure cooker. Cook on medium-high heat for 3 whistles, then turn off the flame and let the pressure release naturally.
Stir in the tamarind paste with the sambar so it is mixed well. Garnish with cilantro and serve.
Tamarind paste: If you don't have tamarind paste, you can soak seedless tamarind in 1/4 cup water and microwave for 30 seconds. It will become soft enough to use.Sambar powder: If you don't have sambar powder, grind all these spices - 2 whole red chilies, 1 tsp coriander seeds, 1/2 tsp fenugreek seeds, 1 tsp cumin seeds, 1/2 tsp whole black peppers, 1/2 tsp turmeric powder.Jaggery or Sugar: I did not add any jaggery or sugar in this recipe. However you can add some to your taste after pressure cooking. Start with 1-2 teaspoon of grated jaggery, and increase to taste. Pot-in-pot veggies for sambar: With the method above of cooking vegetables along with the dal, the vegetables get well cooked and mix together with the lentils. However if you like your veggies cooked, but not completely mushed with the lentils, use pot-in-pot method to cook the vegetables. Add the ingredients for sambar, except the veggies in the instant pot steel insert. Then in a steamer basket, add veggies. Close lid and pressure cook the sambar. After the pressure is released, take the steamer basket out carefully. Now you can whisk the lentils if needed to make the sambar completely smooth. Then add the steamed veggies.