Char the onion and ginger over an open flame or under a broiler until blackened and fragrant.
In a large pot, toast the star anise and cinnamon stick for 1-2 minutes until aromatic.
Add the beef bone broth, charred onion, charred ginger, and fish sauce to the pot and simmer for 20 minutes.
While the broth simmers, cook the rice noodles according to package directions, then drain and set aside.
Strain the broth to remove the solids and return the clear liquid to the pot, bringing it to a rolling boil.
Place the cooked noodles in a large bowl and top with the raw, thinly sliced beef eye of round.
Pour the boiling hot broth over the beef and noodles to cook the meat instantly.
Garnish with bean sprouts, Thai basil, jalapeno slices, salt, pepper, and a squeeze of lime before serving.