Pieter Malan struck a career-best 264 as the Cobras edged closer to a big victory over the Knights in Cape Town on Thursday.
Malan achieved his highest first-class score in the process, guiding the Cobras to a mammoth 523-8 before the Cape side declared.
Kyle Verreynne also once again starred with the bat, reaching a brilliant century of his own before departing for 108.
George Linde then spun the Knights into further trouble, picking up four wickets as the Knights battled to stumps on 106-7, still trailing the Cobras by 236 runs.
In Durban, the Dolphins also closed in on a resounding victory over the Warriors, who managed 345 in their second innings.
Edward Moore scored an excellent 155 but the rest of the Warriors batting lineup failed to add value down the order. Keshav Maharaj was once again the top performer with ball, claiming 6-93. Chasing only 112 runs for victory, the Dolphins saw out the day on 8-0.
Bad light ended play early in Johannesburg where the Lions and Titans are locked in a tight contest. Aiden Markram reached another century for the Pretoria outfit, but Lutho Sipamla and Kagiso Rabada each bagged five wickets to dismiss the Titans for 202.
Reeza Hendricks then fell four runs short of a century as the Lions batted out the day on 247-6, a lead of 251.