In a large pot, add broth, onion, garlic, ginger, cinnamon, star anise, and cardamom.
Bring to a boil, then reduce heat and simmer for 30 minutes. Strain to remove solids.
Stir in sugar and fish sauce. Adjust seasoning if needed.
Soak rice noodles in hot water for 8-10 minutes until soft. Drain and rinse.
Divide noodles into bowls. Top with raw beef slices.
Ladle hot broth over the beef (it will cook thinly sliced beef instantly).
Add bean sprouts, herbs, and a squeeze of lime.
Serve with Sriracha or hoisin sauce on the side.
