Broth Preparation: Place beef bones in a large stockpot. Add water and apple cider vinegar to help extract nutrients from the bones. Bring to a boil, then reduce heat to a simmer. Skim off any foam that rises to the top.
Simmering: Allow the broth to simmer gently for 12- 24 hours. This long simmering process extracts the maximum amount of nutrients and flavors from the bones, creating a rich and savory broth.
Seasoning the Broth: Add salt to the broth, adjusting the amount to your taste preference. If using, add black pepper at this stage.
Straining: After the broth has finished simmering, strain it through a fine-mesh sieve to remove the bones and any impurities. Return the clear broth to the pot and keep it hot.
Preparing the Beef: Arrange the thinly sliced beef on a plate. The beef should be thinly sliced so it will cook quickly when added to the hot broth.
Assembling the Pho: Place some thinly sliced beef in a bowl. Ladle the hot broth over the beef, which will cook the meat instantly.
Serving: Serve the carnivore pho immediately, ensuring the broth is hot enough to gently cook the thin beef slices upon serving.