Turn Instant Pot to saute, add ½ tablespoon extra virgin olive oil, and let heat briefly.
To the heated oil, add in 1 small yellow onion (minced), ⅓ cup diced celery, and ½ cup diced carrots and saute for 2-3 minutes, or until the vegetables begin to soften.
Add in 1 cup dried brown or green lentils and 2 teaspoons minced garlic and saute for an additional 1 to 2 minutes. Turn Instant Pot OFF.
Add 4 cups vegetable broth and scrape up any browned bits on the bottom of the instant pot to prevent a burn warning.
Season with 1 teaspoon oregano, 1 teaspoon coriander, 1 teaspoon cumin, 1 teaspoon kosher salt, and 2 bay leaves. Top with 1 (15-ounce) can crushed tomatoes and 1 (15-ounce) can diced tomatoes.
Place the lid on the pressure cooker and be sure the vent knob is pointed towards sealed. Set cook time for 15 minutes on high pressure by hitting manual or pressure cook and using the +/- buttons to adjust the timing.
Once the cook time has elapsed, allow pressure to release naturally.
Once the pressure has been released, remove the lid. Give the soup a stir, discarding the bay leaves as you come across them. Stir in the 1 tablespoon fresh lemon juice or balsamic vinegar and serve.
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Notes
Lentils: Use dried green or brown lentils, not red or yellow lentils as they can become mushy. Note on Salt: If your broth and tomatoes are not low sodium, cut the salt down to ½ teaspoon.Tomatoes: Feel free to use all crushed tomatoes or all diced tomatoes instead of a combination of the two.Storage: Lentil soup will keep in an airtight container in the fridge for 4-5 days. Alternatively, you can freeze this soup in freezer-safe containers, leaving 1 inch of room for expansion for up to 3 months.Cooking at high altitude? Use the conversion chart for cooking in the Instant Pot at High Altitude.