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, cinnamon stick, and cloves over medium heat for 2 minutes until aromatic.
Add the beef bone broth, charred onion, charred ginger, fish sauce, and coconut sugar to the pot.
Simmer the broth gently for 20 minutes to allow the spices to infuse.
While the broth simmers, cook the rice stick noodles according to the package instructions, then drain and set aside.
Strain the broth through a fine-mesh sieve to remove the solids and return the clear liquid to the pot, bringing it to a rolling boil.
Place the cooked noodles in a large serving bowl and top with the raw, thinly sliced beef eye of round.
Pour the boiling broth directly over the beef to cook it instantly, then season with sea salt and black pepper.
Garnish the soup with bean sprouts, cilantro, Thai basil, and a squeeze of fresh lime juice before serving.