Char the onion and ginger over an open flame or in a dry pan until fragrant and slightly blackened.
In a medium pot, bring the beef bone broth, star anise, cinnamon, charred onion, and ginger to a simmer for 15 minutes.
While the broth simmers, cook the rice noodles according to package directions, then drain and set aside.
Thinly slice the raw beef eye of round against the grain into paper-thin pieces.
Strain the aromatics from the broth and stir in the fish sauce, sea salt, and black pepper.
Place the cooked noodles in a large bowl and top with the raw beef slices.
Pour the boiling hot broth directly over the beef to cook it instantly, then garnish with bean sprouts, basil, jalapeno, and a lime wedge.