In a medium pot, combine the beef bone broth, star anise, cinnamon stick, sliced ginger, and white onion.
Bring the mixture to a boil, then reduce the heat and simmer for 15 minutes to allow the aromatics to infuse the broth.
While the broth simmers, cook the rice noodles according to the package directions, then drain and place them into a large serving bowl.
Thinly slice the raw flank steak across the grain into very thin pieces.
Remove the star anise, cinnamon stick, and ginger pieces from the broth and stir in the fish sauce, sea salt, and black pepper.
Arrange the raw beef slices on top of the cooked noodles in the bowl.
Pour the boiling hot broth directly over the beef slices to cook them until tender and pink.
Garnish the bowl with bean sprouts, fresh cilantro, Thai basil, and a squeeze of lime juice before serving.