Bautista Delguy crossed for two tries as the Pumas – who suffered a 34-21 defeat on South African soil a week ago – punished a mixture of poor discipline and weak tackling to score 27 first-half points.
The visiting Springboks scored the opening try of the game, captain Siya Kolisi bursting clear to reach the line, but the hosts hit back with three scores of their own to seize control by the interval.
After Delguy’s brace prior to the break, fellow winger Ramiro Moyano touched down early in the second half as Mario Ledesma's side extended their lead.