In a large pot, heat the olive oil over medium heat. Add the chopped onion, garlic, carrots, and celery. Sauté until the vegetables are softened, about 5-7 minutes.

Stir in the rinsed lentils, cumin, thyme, salt, vegetable broth, and bay leaf. Bring to a boil.

Reduce the heat to low and let the soup simmer for about 25-30 minutes, or until the lentils are tender.

Remove the bay leaf and stir in the lemon juice. Adjust seasoning if necessary. Serve hot, garnished with fresh parsley.