- Heat butter over medium-high heat in a Dutch oven and add onion, celery and carrots. Cook covered for 7 minutes. Stir in garlic and cook 2 minutes longer.
- Stir in chicken broth, tomatoes, lentils, soy sauce, cumin, turmeric, black pepper and sprig of rosemary. Bring to a boil. Reduce heat to medium-low and simmer for 20 minutes with lid cracked slightly, or until lentils are tender. Stir in spinach and cook an additional 5 minutes to wilt. Remove rosemary. Ladle into bowls and serve hot.