Dry‑roast the aromatics: Heat a dry skillet over medium‑high. Place onion and ginger cut‑side down and cook until deeply browned and fragrant. Flip once to lightly toast the other side.
Toast the spices: In the same skillet, add cinnamon, star anise, cloves, and coriander seeds. Toast 1–2 minutes until fragrant.
Optional: Blanch the bones for a cleaner broth:
Cover bones with water in a pot. Boil 5 minutes, then drain and rinse. Skip this step for the fastest version — broth will still be delicious.
Build the broth: Add bones, dry‑roasted onion, dry‑roasted ginger, toasted spices, fish sauce, sugar, salt, and water to the pressure cooker.
Pressure cook: Cook on High Pressure for 45 minutes, then allow natural release (15–20 minutes).
Strain: Remove bones, aromatics, and spices. Strain broth through a fine mesh strainer for clarity.
Season to finish: Taste and adjust with more fish sauce, salt, or sugar. Traditional phở broth is balanced and gentle — final seasoning happens in the bowl.
Assemble bowls: Add cooked noodles to bowls. Top with thinly sliced raw beef, onions, green onions, and cilantro. Ladle hot broth over the beef to cook it.
Serve: Add lime, sprouts, jalapeño, and sauces to taste.