I have been experimenting with my D7K in Commander mode.
D7K with 50mm F1.8D. SB900 off to the left at 45 degrees and fired bare at 1/2 power. Built in flash turned off but used to trigger SB900.
Evening sun from right. Under exposed background. The star shape highlight on the bridge of the bass is a kick back from the bare flash.
Straight from camera, just a crop.