Domestic shorthair. You can get a shorthaired black cat MANY different ways -- no guarantee that it's a Bombay. Bombays are fairly rare still, and reputable breeders don't let their Bombays go around mating with stray cats.

A Bombay might not look like a specific breed, but it is just as specific as any other, with a specific body type, head shape, eye shape, eye color, and coat. Your cat's face shape, eye shape, and body type are very different from a Bombay -- which have a very rounded look about them, and have compact bodies like a Burmese. Your gorgeous baby looks just like a beautiful domestic shorthair.