For the first cooking cycle:< In the Instant Pot, combine the toor dal, water, tomatoes, onion, sugar, salt, turmeric, cayenne, and spice mix. Stir to combine.
Secure the lid on the pot. Close the pressure-release valve. Select MANUAL or PRESSURE COOK and set the pot at HIGH pressure for 10 minutes. At the end of the cooking time, allow the pot to sit undisturbed for 10 minutes, then release any remaining pressure. Using an immersion blender, puree the mixture directly in the pot until smooth.
For the second cooking cycle: Add the water, pearl onions, green beans, and tamarind concentrate to the pot.Secure the lid on the pot. Close the pressure-release valve. Select MANUAL or PRESSURE COOK and set the pot at HIGH pressure for 2 minutes. At the end of the cooking time, quick release the pressure.
For the tadka: In a small skillet, melt the ghee over medium-high heat. Add the mustard seeds, chiles, and curry leaves. Stand back and allow the mustard seeds to sizzle and spatter for about 30 seconds. Pour the hot flavored ghee into the sambhar and mix well.Divide sambhar among four serving bowls and garnish with cilantro.