I think i agree with Stacy on this one; the fact that you're a black writer doesn't mean that your work should be defaulted to the african-american genre, regardless of whether or not there are black characters in them. I don't believe that your race should have anything to do with your writing - there are so many non-black authors whose origin are not caucasian, yet their works are not necessarily classified as, say, Indian or Mexican literature, unless, ofcourse, the works are specifically themed as such.
Like Stacy mentioned, books by authors like Tony Morrison, Alice Walker, Donna Hill, Octavia Butler, Terri McMillan are what can be without a doubt tagged as 'black fiction', because their plots and themes are centered around being black and experiencing life as a black person.