Non-spinning backfist KO?

Does anyone know of an MMA fight that was ended by a KO/TKO due to a backfist punch? A regular, non-spinning backfist. Like using your right hand to hit your opponent on the right side of his face, swinging from your left to your right. Or kinda like a bitch-slap, but with a closed fist.

I can't recall ever seeing this happen in a fight, and I'm wondering if it's even possible to generate enough power without spinning.