In Huế itself it's simply called bún bò; the 'Huế' was added elsewhere in Vietnam to say where it came from.
Round rice noodles sit in a broth built from beef and pork bones simmered for hours with lemongrass, chili oil, and fermented shrimp paste, topped with sliced beef shank, cubes of congealed pig blood, and pork knuckle. Street stalls across Huế ladle it out from huge pots, and it's eaten any time of day, not just at breakfast.