Heat the olive oil in a large saucepan over medium heat. Add the onion and cook, stirring occasionally, until soft and translucent, about 5 minutes.

Add the garlic, cumin and coriander, and sauté for another minute, until the garlic becomes very fragrant.

Stir in the lentils, broth and tomatoes. 

Bring the liquid to a boil, lower the heat to a simmer, and allow to continue simmering, uncovered, until lentils are soft, about 20 minutes. Thin the soup with some water if it becomes too thick while simmering.

Stir in the lemon juice and harissa (if using). Season the soup with salt and pepper to taste.

Ladle into bowls and top with parsley and/or cilantro.

Press the "sauté" button on your Instant Pot and add the oil.

Give the oil a minute to heat up, then add the onion. Cook the onion for about 3 minutes, stirring occasionally, until soft and translucent.

Add the garlic, cumin and coriander, and sauté for another minute, until the garlic becomes very fragrant. Press the "cancel" button.

Stir in the lentils, 4 cups of broth, and tomatoes.

Place the lid on your Instant Pot and set the valve to the "sealing" position. Press the "pressure cook" or "manual" button and set the pressure to high. Set the soup to cook for 10 minutes.

When the soup has finished cooking, carefully move the valve to the "venting" position. Let the pressure release completely.

Remove the lid from the Instant Pot. Stir in the lemon juice and harissa (if using). Season the soup with salt and pepper to taste.

Ladle into bowls and top with parsley and/or cilantro.