Using fill flash ? Hmm... not exactly. As u can see the flash is overpowering. I did not achieve the effect I wanted through auto flash, so manual I went as suggested by Amfibus. Basically, under expose the background and use a small aperture to get the star effect of the sun, and than blast the flash at whatever output u want.
I didnt think that was flare, but ghosting in fact. I was using a Sigma 20mmf1.8 EX DG, which I reckon everyone using a 19-35 or 18-35 should have, because its such a magnificent beast.