Place the halved onion and sliced ginger under a broiler for 5 minutes until charred and fragrant.
In a large pot, combine the beef bone broth, charred onion, charred ginger, star anise, and cinnamon stick.
Bring the broth to a boil, then reduce heat and simmer for 20 minutes to infuse the flavors.
While the broth simmers, cook the brown rice noodles according to package directions, then drain and set aside.
Thinly slice the beef eye of round against the grain into paper-thin pieces (freezing for 15 minutes beforehand makes this easier).
Stir the fish sauce, sea salt, and black pepper into the broth, then remove the whole spices and onion pieces.
Divide the cooked noodles into a large bowl and top with the raw, thinly sliced beef.
Ladle the boiling hot broth directly over the beef to cook it instantly in the bowl.
Top with bean sprouts, fresh basil, cilantro, jalapeño slices, and a squeeze of lime before serving.