Place the halved onion and ginger slice under a broiler for 5 minutes until slightly charred to release deep, smoky flavors.
In a medium pot, toast the star anise and cinnamon stick over medium heat for 2 minutes until aromatic.
Add the beef bone broth, charred onion, ginger, fish sauce, and coconut aminos to the pot and bring to a gentle simmer for 20 minutes.
While the broth simmers, cook the brown rice noodles according to package directions, then drain and set aside.
Place the eye of round steak in the freezer for 15 minutes to firm up, then slice it against the grain into paper-thin pieces.
Strain the broth to remove the solids and return the clear liquid to a boil, seasoning with sea salt and black pepper.
Divide the cooked noodles into a large bowl and arrange the raw beef slices on top.
Pour the boiling broth over the beef to cook it instantly, then garnish with bean sprouts, cilantro, Thai basil, jalapeño, and a squeeze of fresh lime.