In a large pot, heat oil over medium heat. Add onions, garlic, carrots, celery and cook for 7-8 minutes until slightly caramelized.
Add tomatoes, bring to a simmer and cook for 6 minutes. Add vegetable broth, bay leaf, season with salt and pepper. Bring liquid to a boil and reduce heat to low. Cover with lid and simmer for 10 minutes.
Remove lid and stir in lentils. Simmer stew for 30 minutes until slightly thick. Turn off burner and cover with lid. Let stand for 5 minutes. Stir and serve topped with parsley and pita bread for dipping.