The win brought an end to a dismal month in which Pirates suffered two defeats and a disappointing stalemate, as the chase for league honours seemed to evade the Soweto giants.
The losses included a defeat to Sundowns a fortnight ago, when Downs walked away with a 1-0 win at Orlando Stadium on February 8.
But on Tuesday, Masuku's 37th minute decider proved enough as Pirates showed signs of the kind of form which saw them compete in the final of the Caf Champions League in November last year.
With a massive crowd packed into Loftus, the home side went on the attack early on as Sundowns looked for a dominant early display.
Pirates, through, were able to subdue the Brazilians as the opening 15 minutes passed without any clear scoring opportunities.
Despite a frantic first few minutes, neither team were able to come up with the necessary spark in the final third as chances went begging.
Ramagalela was the first to test the goalkeeper as he thumped an effort from distance and forced Senzo Meyiwa into a good save as he tipped the shot over the bar and out of danger in the 30th minute.
But the Buccaneers had other ideas and eight minutes from the break, Masuku tapped home to hand the visitors the opener.
Helder Pelembe showed great skill on the far side as he beat three defenders on his way to delivering a superb ball into the area, before Masuku snuck behind the defensive line and side-footed a simple finish into the back of the net.
Sundowns followed up the opener with their best chance on the stroke of half-time when Hlompho Kekana was denied a well-hit free-kick strike by Meyiwa, parrying away the shot and sending the ball out for a corner.
In the end, Sundowns would be denied the opportunity of closing the gap on log-leading Kaizer Chiefs to six points.