1.Combine carrot, onion, 1 teaspoon salt, spices, chilli and sugar, 1 tablespoon lime juice and 3 cups water in a large saucepan. Bring to boil, stirring occasionally. Reduce heat, cover and simmer for 30 minutes or until carrots are tender.
2.With a blender, puree soup. Season to taste and cool to room temperature. Stir in another 2 cups cold water and chill until very cold.
3.Stir in remaining lime juice and check seasoning. Top with coriander and serve with pappadums.