Rinse the green moong dal under running water several times until the water runs clear.
Set the Instant Pot to the 'Sauté' mode and add 2 tablespoons of oil once hot.
Add the cumin seeds and let them sizzle for a few seconds until fragrant.
Add the chopped onions and sauté until they turn golden brown.
Stir in the minced garlic and grated ginger and sauté for another minute.
Add the chopped tomatoes, turmeric powder, coriander powder, slit green chilies, and salt. Cook until the tomatoes soften.
Add the rinsed moong dal and mix well with the onion-tomato-spice mixture.
Pour in 3 cups of water and give everything a good stir.
Close the lid of the Instant Pot and set it to 'Pressure Cook' on high for 15 minutes.
Once the cooking time is complete, allow for a natural pressure release for about 10 minutes, then carefully release any remaining pressure.
Open the lid, stir the dal, and taste for seasoning. Adjust salt if necessary.
Stir in the garam masala and let it rest for a few minutes before serving.
Garnish with fresh cilantro if desired, and serve hot with rice or flatbreads.