Add dry lentils to a large bowl and cover completely with water. Allow them to soak at least two hours or overnight, then rinse and drain before using.
In a large dutch oven or pot, heat olive oil over medium heat, then add carrots, celery, onion, and garlic. Cook, stirring frequently, until veggies start to soften (about 8–10 minutes).
Add the tomato paste, oregano, salt, cumin, and bay leaf, and stir to coat.
Pour in the vegetable broth and stir.
Add soaked lentils and bring to a boil.
Reduce heat to low, and allow to simmer 30 minutes or until lentils and veggies are tender.
Serve warm with additional olive oil if desired.
Notes
This soup is very flavorful and very filling, almost like a stew because the lentils absorb lots of liquid.
Add additional broth if you want it to be more soupy.
This soup is great paired with crusty bread. It also reheats well from fridge or freezer.
Craving more veg-friendly recipes? Shop our collection of vegetarian and vegan cookbooks, including our new Vegan Thanksgiving and Vegan Christmas cookbooks!