The prohibition is against meat and dairy simultaneously.
Not only that, but the kosher requirements (no dairy and meat together), depending on how kosher you are, also to apply to the plates the meal is served on, the equipment the meal is cooked on, and food storage areas; you need strictly segregated facilities, and washing between uses does not make it kosher. The requirements are strict to the point where rabbis have to regularly certify kosher restaurants as kosher.
https://www.thedailymeal.com/eat/what-exactly-american-chees...