This is a variety of cauliflower called the "Romanescu". IT's been painted to show off its many different fractal fibonacci spirals.
The image was sent along by Beletseri (thanks!), from
this gent's page.
I've never seen or even heard of this variety before, but the gent says that such patterns are visible on all cauliflower if you look hard enough. I guess I haven't looked hard enough. I will now.
Googling for Romanescu suggests that it is rare, and is a term applied to cabbage and broccoli as well, and that those vegetables also have the patterns.