Finely chop the onion, carrot, and celery.
Soak the lentils in water to prepare.
Drizzle olive oil into a pot and sauté the chopped vegetables.
Add the tomatoes and cook together.
Add the lentils, water, and bay leaf.
Season with salt and pepper.
Once it comes to a boil, reduce to medium-low heat and simmer for 30 minutes.
Remove the bay leaf and your soup is ready.