Begin by making your beef bone broth as explained above. You can either add in your spices during that process or separate out some broth and continue with the recipe as follows.Simmer your broth in a pot on the stove with your spice blend added in. I usually put my spices into a cotton bag to make for easier straining later on. As you simmer the broth, skim off any foam that comes to the top.Meanwhile, wash both your ginger root and your (peeled) onion, slice them in half, and place them on a baking sheet in your oven.Broil them until they get dark on top.Once your ginger and onion are ready, add them to your simmering broth to give it more flavor.Keep simmering for around half an hour, or until the soup has absorbed the flavors of the spices to your liking. At this point, I like to add in the fish sauce to taste. I start by adding one tablespoon and then taste it and then add more, a little bit at a time, if I think it needs it.Remove your broth from the stove and remove the ginger and onion. I like reserving the onion for adding back to the soup later on. Strain the broth if necessary to get out any of the remaining spices, and put the broth back into the pot.Add your zucchini noodles and once again simmer it, this time with the noodles, until they have reached the desired level of being cooked. I usually only cook it for about a minute or two.Meanwhile, I like to sear the outside of the beef that I will be adding to the pho. Many people like to thinly slice it raw and add it to the soup that way. I prefer to sear the edges first, leaving it very rare inside.When you are ready to serve the soup, add the broth and some zucchini noodles to each bowl. Thinly slice the seared beef and place the thin slices on top of the soup. The heat of the soup will help lightly cook the thin slices.Serve with garnishes that each person can add to their bowl of soup as desired.