1. Roast the beef bones, onion, and ginger in the oven at 400°F for 30 minutes.
2. Transfer to a large pot, add water, and bring to a boil. Skim off any foam.
3. Add star anise, cinnamon, coriander seeds, fennel seeds, salt, and sugar. Simmer for 2 hours.
4. Strain the broth and return to the pot. Add fish sauce.
5. Cook rice noodles according to package instructions.
6. Divide noodles into bowls, top with raw beef slices, and pour hot broth over to cook the beef.
7. Serve with bean sprouts, lime wedges, fresh herbs, green onions, and chili pepper.