In a Dutch oven, heat oil over medium heat. Add sausage and cook until browned. Remove and set aside.
Stir in the onion, carrot, and celery. Cover and cook for 8 minutes, stirring occasionally. Remove the lid and continue cooking for an additional 10-15 minutes. Until the vegetables are softened. Add the garlic and heat until fragrant.
Stir in the fire roasted tomatoes, thyme, cumin, chicken broth, sausage, and lentils.
Bring to a boil and simmer for 45-50 minutes or until the lentils are tender.
Stir in a handful of spinach.
Salt and pepper to taste.
Garnish with grated Parmesan cheese and serve.