Prepare ginger. Peel, halve lengthwise and smash it.
Bring broth, ginger, lime zest and five-spice powder to boil in dutch oven over med-hi heat. Add noodles and cook until nearly tender, about 5 minuts.Stir in beef. Simmer until cooked thru and noodles are completely tender, about 2 minutes.
Off heat, stir in fish sauce, chili-garlic sauce and lime juice. Remove ginger and zest with slotted spoon. Stir in scallions and cilantro; serve.