Sift through lentils to ensure there are no other particles! Rinse thoroughly – draining about 4 or 5 times until water runs fairly clear.
Leave the lentils soaking in some water, enough to cover it while you prepare your masala (onion and tomato mixture).
Heal oil for one minute over medium heat in a small pot. Once the oil is shimmering, add whole cumin seed. You want to just lightly toast the seeds, not burn them. After about 30 seconds add onion, garlic and ginger.
Cook onion mixture for 10 - 15 minutes. They should be very well cooked and almost on the brink of caramelizing!
Add diced tomatoes, cayenne, turmeric, black pepper and salt if using (if baby is > 1 year of age) and sauté for another 10 - 15 minutes. The mixture should basically look like a wet mush! You want to be constantly stirring it. At this point you may need to turn down the heat to prevent burning on the bottom of your pan. This is where the magic of patience takes place.
In the meantime, rinse the lentils one final time and add into Instant Pot with 6 cups of water.
Add your masala into the Instant Pot and give this a final stir.
Secure the lid, place to SEALING and cook on Manual setting for 25 minutes.
Once completed, natural release for 10 minutes and then quick release.
Taste and adjust seasonings as you wish or add more water to thin out.
Garnish with cilantro and garam masala.