Rub the beef with the garlic powder, paprika and salt and roast until medium rare, about 1 hour 10 minutes. Let cool, then thinly slice.
Bring 2 gallons of water to a boil in a large pot. Drop in the noodles and cook for 1 minute 30 seconds, using tongs to separate and fluff the noodles in the water. Drain and divide among 6 bowls. Top each bowl with sliced beef, the cilantro, jalapenos and radishes. Slice the soft-boiled eggs in half lengthwise and sprinkle with chili flakes before adding one half to each bowl. Pour enough hot broth into each bowl, so that there is twice as much broth as noodles.