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 over medium heat for 1-2 minutes until aromatic.
Add the beef bone broth, charred onion, ginger, and fish sauce to the pot; bring to a boil then simmer for 20 minutes.
While the broth simmers, cook the rice noodles according to package directions, drain, and set aside.
Thinly slice the raw beef sirloin against the grain into paper-thin pieces.
Strain the broth to remove the solids and return the clear liquid to a rolling boil.
Divide the cooked noodles into a deep bowl and arrange the raw beef slices on top.
Pour the boiling broth directly over the beef to cook it instantly, then season with sea salt and black pepper.
Top with bean sprouts, cilantro, Thai basil, and jalapeño slices, serving with a fresh lime wedge on the side.