First make the stock. Add all of the vegetable scraps to a large pot and cover with water, bring to a boil and then turn down to simmer for 30 to 45 minutes.
Heat a large soup pot over medium heat. Add the oil and then the onion, celery and cumin. Season with salt and pepper and cook for 5 to 7 minutes.
Stir in the lentils, broth and tomatoes. Bring to a boil and turn down to simmer for 40 minutes. When done cooking, allow to cool slightly and puree 3 cups of the soup with an immersion blender and then stir back into the pot. Season as needed.