1. In slow cooker, combine onion, carrots, garlic, lentils, cumin, ginger, cinnamon, 1/2 tsp. salt, broth and 3 cups water. Cover and cook on low until lentils and vegetables are tender, 6 to 7 hours.
2. Stir in spinach, cover, raise heat to high and cook for 20 minutes. Stir in lemon juice, season with salt and serve.