Lentil Soup with Mustard Oil and Tomato-Chive Topping

Heat 1 tablespoon oil in heavy large pot over medium heat. Add next 9 ingredients; sauté until vegetables begin to brown, about 12 minutes. Add 4 coarsely chopped tomatoes and turmeric; stir 2 minutes. Add broth and lentils; bring to boil. Reduce heat to medium-low; cover and simmer until lentils are very tender, about 45 minutes. Season with salt and pepper. Puree soup in batches in blender. Return to pot. (Can be made 2 days ahead. Chill until cold, then cover and keep chilled. Rewarm soup before continuing.) Mix 3 finely chopped tomatoes and chives in bowl. Heat 2 tablespoons oil in heavy medium saucepan over medium-high heat. Add mustard seeds; cook until seeds darken and begin to pop, about 2 minutes. Pour into small bowl. Ladle soup into bowls. Top with mustard oil and tomato-chive mixture. *Available at Latin American markets and some specialty foods stores.