Australia captain Michael Clarke brought up his 27th test century on Sunday to ram home the tourists' advantage over South Africa in the third and decisive test, moving to 434-4 at lunch on day two.
Clarke survived a fierce barrage of short bowling from Morne Morkel on the opening day of the match, and was rewarded for his resilience as he moved to an unbeaten 137.
Steve Smith was the only batsman to fall in Sunday's first session at Newlands, as he chopped a wide Dean Elgar delivery onto his stumps to depart for 84.
South Africa was handicapped by the continued unavailability of fast bowler Dale Steyn, who failed to overcome a hamstring strain picked up on the opening day.
With low cloud around Newlands at the start of the day and a second new ball in hand, that was a major blow for the hosts, who failed to make early inroads.
Clarke began the day on 92 not out, but spent 25 deliveries on 99 before driving a Vernon Philander delivery through the covers for four to go to three figures.
The Newlands crowd gave the Australian captain a rousing ovation, having seen him get hit on the elbow, jaw, shoulder and hand during a brutal spell from Morkel on Saturday.
While Clarke was struggling to find his 100th run, Smith was having no trouble scoring. He drove Philander back over his head for six, and then slashed Morkel over extra cover for another maximum.
Such brilliance made his lapse in concentration against part-time spinner Elgar all the more disappointing.
Shane Watson accompanied Clarke to the interval on 21 not out after a productive session in which Australia added 103 runs.