The Brazilians scored on either side of the break to extend their unbeaten run in the Absa Premiership to 11 games and regain their place atop the league standings.
SuperSport United, still hurting from their defeat to Polokwane City, looked a determined side from the onset and a one-two between Jeremy Brockie and Dove Wome almost caught Sundowns napping after two minutes.
The Togo attacker had a sight of goal, but rushed his shot – with Denis Onyango approaching – he sent his chip effort wide.
‘Downs first attempt fell to Khama Billiat on 14 minutes. With his teammates gathered in the area the Zimbabwean looked sure to swing in his free-kick, but instead went direct at goal, Williams though was alert to the danger.
Keagan Dolly then got in behind the Matsatsantsa defensive line before drawing a save out of Williams, Billiat pounced on the rebound, but could only manage to direct his shot across the face of goal.
With the half coming to an end Gordon Igesund would’ve been content with his sides performance, but a blooper by Williams gifted ‘Downs a corner-kick from which they scored.
The SuperSport stopper’s clumsy mistake punished – Kekana floating in unmarked to head home Dolly’s inch-perfect cross on 43 minutes.
Things went from bad to worse for SuperSport two minutes following the interval. The combination of Dolly and Billiat dispossessing Dean Furman, the latter setting up Castro for an easy tap-in.
Were it not for Williams Billiat would have had a quick-fire brace before the hour, the South African stopper with two top saves to deny the former Ajax Cape Town winger.
Castro also unlucky to see his header attempt flash inches wide in an unstoppable period of play by the hosts.
David Mathebula burst into the area before sending his attempt wide of goal with Onyango rooted to his spot late on as SuperSport searched for a way back into the game.
In the end though Sundowns were deserved winners, yet again underlining why so many have made them favourites for the title this season.