Green’s Dictionary of Slang

(US) a full range of unrestrained sadomasochistic activities as practised in a sex session; thus beefsteak, hold the onions, a modified version with no real pain inflicted.

1987

interview in Murray & Murrell Lang. Sadomasochism (1989) 38: It’s pretty odd but it [i.e. beefsteak and onions] means S and M, no holds barred [...] [Beefsteak, hold the onions] refers to the lighter stuff — no real pain.