Char the onion and ginger over an open flame or under a broiler until slightly 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, ginger, and fish sauce to the pot and simmer for 20 minutes.
While the broth simmers, prepare the rice noodles according to package directions and set aside.
Thinly slice the raw eye of round beef against the grain (pro tip: freeze for 15 minutes first for easier slicing).
Strain the broth to remove the solids and return the clear liquid to the pot, seasoning with salt and pepper.
Place the cooked noodles in a bowl, top with the raw beef slices, and pour the boiling hot broth over the top to cook the beef instantly.
Garnish with bean sprouts, cilantro, sliced green onions, jalapeño, and a squeeze of fresh lime.