bas rutten did it on frank shamrock. The spinning back fist isnt a complicated move. The actual move is easy the problem is people teach it wrong so it becomes very telegraphed when you do it the wrong way. Most people spin around and have it come around with them like a pimp slap. Thats the wrong way to do it.
thats the wrong way to do it but the most common way you see it.
the proper way to throw it is when you spin you keep your guard up and then when your fist is in range again you throw a back fist strike.