Char the halved onion and ginger over an open gas flame or under a broiler until blackened and fragrant.
In a large heavy-bottomed pot, toast the star anise and cinnamon stick over medium heat for 2 minutes until aromatic.
Add the beef bone broth, charred onion, and charred ginger to the pot and bring to a gentle simmer for 20 minutes.
While the broth simmers, soak the rice stick noodles in a bowl of hot water until tender, then drain and set aside.
Place the eye of round beef in the freezer for 15 minutes to firm up, then slice against the grain into paper-thin pieces.
Strain the broth through a fine-mesh sieve to remove the solids and return the clear liquid to the pot.
Stir the fish sauce, sea salt, and black pepper into the hot broth and adjust seasoning to taste.
Divide the prepared noodles into a large serving bowl and layer the raw beef slices evenly across the top.
Pour the boiling hot broth directly over the beef to cook it instantly and serve immediately with bean sprouts, herbs, jalapeño, and lime.