In the stainless steel bowl of the Instant Pot, combine the onion, carrots, celery, diced tomatoes along with their juices, garlic, cumin, curry powder, cayenne (if using), lentils, salt, pepper, and water.: The moment you add these ingredients together you will notice a faint, fresh vegetable aroma and the sharpness of the garlic and spices. Because everything goes in raw, the lentils absorb flavors from the start, producing a cohesive broth. Stir gently to distribute the spices so pockets of intense flavor do not form. Common mistakes here include uneven chopping or adding too much salt initially, which can be hard to correct under pressure. Ensuring the lentils are rinsed and the vegetables are uniformly chopped promotes even cooking and a balanced mouthfeel.
Secure the lid and move the steam release valve to Sealing. Use the Manual or Pressure Cook button to cook for 10 minutes at high pressure. It should take roughly 15 minutes for the pot to come to pressure, so the screen will read ON until then.: As the pot comes to pressure you will hear soft clicks and the sound of steam beginning to build, a comforting mechanical hum that signals the flavors are melding. The high pressure forces liquid into the lentils , making them tender while concentrating taste. Make sure the valve is set correctly to avoid steam leakage, and resist the urge to open the lid while it presses. A typical slip up is lifting the lid early, which drops pressure and interrupts cooking, resulting in al dente lentils .
When the cooking cycle is complete, allow the pressure to naturally release for 10 minutes, then move the steam release valve to Venting. When the floating valve drops, it's safe to remove the lid.: The natural release period lets the lentils finish cooking gently while the broth settles, preventing sudden agitation that can break the lentils apart. You will notice a quieter kitchen as steam subsides. After releasing, lift the lid carefully away from your face so escaping steam does not cause a burn. A frequent error is forcing a quick release immediately, which can make the lentils splatter and lose texture.
Give the soup a stir to make sure the lentils and vegetables are tender, then stir in the chopped fresh spinach. The greens should wilt quickly in the hot soup. Season with additional salt to taste, then serve warm with slices of lemon or freshly chopped parsley on top, to help brighten the flavor even more.: When you stir, the aroma becomes richer and the broth appears thicker, with the softened lentils lending body. Adding the fresh baby spinach at this point creates a vivid green contrast and a fresh vegetal note. Taste and adjust seasoning, because heat can mute saltiness; a little extra at the end wakes up the entire pot. Avoid over stirring vigorously, which may break down lentils more than desired.
Leftover soup can be stored in an airtight container in the fridge for up to a week.: As the soup cools, flavors continue to marry, and the texture often improves the next day, with a deeper, more integrated profile. Refrigerated, you'll notice the surface may thicken slightly; reheat gently on the stove or in the microwave until steaming. A common oversight is storing hot soup immediately without cooling slightly first, which can raise fridge temperature and affect food safety; cool for a short period before sealing the container.
