The 'Snow White and the Huntsman' director speaks about the woman he cheated with on the DVD's commentary.
The movie boss - who is married to Liberty Ross and has children with the model - was caught enjoying a fling with the 22-year-old actress and calls her ''amazing'' and ''flawless'' in the voiceover.
In the motion picture, Liberty plays Kristen's character's mother Queen Eleanor, and when she appears on screen Rupert says ''That's actually my wife!''
This was the first movie Rupert directed and it was on set that the pair got to know each other.
He exclaims as the woman he cheated on his wife with makes her onscreen debut: ''First time we see Kristen Stewart.
''This is the first dialogue I shot with her; I said maybe you do a prayer. Her accent was flawless; she did such an amazing job on it.''
Rupert continues to praise the 'Twilight' actress, who split form boyfriend Robert Pattinson as a result of the cheating scandal.
He says: ''Kristen was amazing. I'd sit down with Kristen at lunch and say, 'What do you think?'''
Kristen made her first public appearance since the July events at the Toronto International Film Festival on Thursday (06.09.12) for the premiere of 'On The Road'.