Heat the olive oil in a large pot or Dutch oven over medium heat. Add the chopped onion, carrots, and celery. Cook, stirring occasionally, for 6-8 minutes, until the vegetables have softened. Add the minced garlic, dried thyme, oregano, and smoked paprika. Cook for another minute until fragrant.

Pour in the vegetable broth and add the can of diced tomatoes (with their juices). Stir everything together. Add the rinsed lentils and the bay leaf.

Bring the soup to a boil, then reduce the heat to low, cover, and let it simmer for 30-35 minutes, or until the lentils are tender.

Remove the pot from the heat and discard the bay leaf. Stir in the balsamic vinegar. Season generously with salt and freshly ground black pepper to taste. Serve hot, garnished with fresh parsley if desired.