Prep the lentils: Rinse the lentils under cool water and pick out any small stones or debris. No soaking needed.
Sauté the base: In a large pot, warm the olive oil over medium heat. Add the onion, carrots, and celery.
Cook 6–8 minutes, stirring, until the onion is soft and translucent.
Bloom the aromatics: Add the garlic, oregano, and cumin (if using). Cook 30–60 seconds until fragrant. Don’t let the garlic brown.
Add lentils and tomatoes: Stir in the lentils and crushed tomatoes until everything is coated and glossy.
Pour in liquid: Add 6 cups of water or broth and drop in the bay leaves.
Bring to a boil, then reduce to a gentle simmer.
Simmer patiently: Partially cover and cook 30–40 minutes, stirring occasionally, until the lentils are tender but hold their shape. Add more liquid if the soup gets too thick.
Season and brighten: Remove the bay leaves. Stir in salt, pepper, and 2 tablespoons red wine vinegar.
Taste and adjust: add more vinegar for tang, a pinch of sugar if the tomatoes are sharp, or more salt as needed.
Finish and serve: Drizzle with good olive oil and sprinkle with chopped parsley. Serve hot with crusty bread and extra vinegar on the table.