Bún riêu cua is a Vietnamese crab noodle soup that is popular in Hanoi. The soup is made from a flavorful broth that is cooked with crab paste, tomatoes, and various spices. It is then served with rice noodles, crab meat, tofu, and fresh herbs. Bún riêu cua is a delicious and comforting dish that showcases the unique flavors of crab.