Peking Duck is the acknowledged name.

beijing kaoya, I'd say... But only about a billion people would understand it. Beijing roast duck sounds better to me. Describing the result of roasting. What the guests really are interested in. Not the means of preparation. Why don't you use the city's official name? - Beijing. Repeating traditional misspelling doesn't make it sound more correct. D., who's always amused hearing the french 'Pekin'.