Add onion and cook, stirring, until softened, about 4 minutes. Stir in curry powder, turmeric, and cayenne; cook, stirring, 1 minute more.
Add lentils and 6 cups water.
Bring to a boil.
Skim to remove foam; simmer lentils, partially covered, 20 minutes.
Add carrots and simmer, partially covered, until tender, about 15 minutes more.
Puree soup in blender, working in batches, and return to the saucepan.
Warm soup on medium heat, stirring, until heated through. Stir in lime juice and chopped cilantro.
Season with salt and pepper to taste.
Add additional water if soup is too thick.
Ladle into bowls and garnish with cilantro sprigs.
Nutrition Facts :
Per Serving: 285 calories, 4 g fat (0.5 g saturated fat), 16 g protein, 75 mg sodium, 46 g carbohydrates, 6 g fiber, 8.5 g sugars (0 g added sugars), 0 mg cholesterol