1. Roast the beef bones, onion, and ginger in the oven at 400°F for 30 minutes.
2. Transfer the roasted ingredients to a large pot, add water, and bring to a boil. Skim off any foam.
3. Add star anise, cinnamon, salt, sugar, and fish sauce. Simmer for 2 hours.
4. Strain the broth and return it to the pot. Keep it hot.
5. Cook the rice noodles according to package instructions. Drain and set aside.
6. To serve, place noodles in bowls, top with raw beef slices, and pour hot broth over to cook the beef. Add bean sprouts, Thai basil, lime wedges, and chili pepper as desired.