What is command? The dictionary defines command as "To exercise dominating, authoritative influence over". The definition is easy, but identifying what contributes to whether you think someone has command is much more complex.
Command is what makes you believe someone is in control, is great at what they do and has the ability to influence people, environments and events around them. It's like style, you know it when you see it.
Command is the secret sauce that gives you confidence that someone is going to get it done. Period.
Lots of stuff goes into whether you think someone has command in a professional situation. How they speak, how they look, whether they really know their stuff, the ability to relate to others from a variety of backgrounds and perspectives, etc. The list of things that go into having command is endless.
It's art. You know it when you see it. And when you don't feel it.
Command is the most important performance factor that impacts every position in your company. Good luck with that, because it's hopelessly subjective.