One serving of this hearty stew has more than half your daily fiber.
Place broth, lentils and bacon in a saucepan. Bring to a boil over high heat. Reduce heat to medium-low; simmer until lentils are tender, about 25 minutes. Remove from heat. Stir in 1 tablespoon of the butter and ¼ teaspoon each of the salt and pepper.
Melt remaining 2 tablespoons butter in a large nonstick skillet over medium-high heat. Add turnips, rutabaga, carrots, onion, thyme and garlic. Sauté until tender, 8 to 10 minutes. Add spinach, vinegar and remaining ½ teaspoon salt and ¼ teaspoon pepper; stir just until spinach wilts, about 1 minute.
Remove and discard bacon. Divide lentils among 4 bowls; top evenly with vegetable mixture.