Set the instant pot to a saute mode. When it is hot, add the cooking oil.
Now temper mustard seeds, chilies and after the seeds splutter, add asafoetida and curry leaves. Save half of this tadka for later use.
Now add onions and saute for a minute. (You don't have to soften the onions)
Add chopped tomatoes and allow it to cook for a while. Once the tomatoes start to lose water and become mushy, add all spices followed by tamarind water.
Give a good mix. Now add all the vegetables, water, salt and mix well.
Lastly, add cooked toor dal and stir well.
Close the lid and set the pot to pressure cook and set the timer for 3-minutes. Since our dal is cooked, you don't have to overcook the veggies. If using raw and soaked dal, then set the timer for 9-minutes. (Remember for this step, the dal must be soaked for at least 2-hours)
After the beep, wait for the natural pressure release. Open the lid and carefully mix the sambar well. Adjust salt and spices if needed. If you like a thin sambar, add 1-2 cups of hot water at this point. If you do so, don't forget to bring the mixture to a boil.
Now add the rest of the tadka and mix well.
Garnish with cilantro and serve hot with rice.