The Scene I recall in the film opens on a flat desert.

Figure dressed in black leather jumpsuit with a motorcycle helmet on, drives a motorbike full speed at another person wearing the same. The second figure has a switch blade and cuts/knocks first figure off bike. When the second figure walks over to the first, now prone, they are tripped by the first who was pretending to be dead. They wrestle shortly and the first figure manages to remove the seconds helmet. It’s a woman with silver paint on her face. First figure is established as a man. He removes her suit and they start to hump. The woman makes strange alien moans. As the guy is going, she gathers the switchblade and is about to stab him in the back, when the knife is kicked out of frame by a new character.

We hear “CUT!” And see that it was part of a commercial or film and the director rushed to kick the knife away believing that the woman was going to really kill the other actor.

Film was in color and possibly a foreign English dub.  I saw it on late night cable in the early 1990’s.