The goals were scored in the second half by Morgan Gould, Dario Monteiro and Brent Carelse.
As expected, Matsatsantsa started to find attacking flow and rhythm as the first half continued and Salmon was unlucky as his effort from outside the box went just wide of Avril Phali's far post after receiving a defence splitting pass from Daine Klate just before the half hour mark.
A few minutes later, their combination created more problems for Cosmos and this time Salmon turned provider for Klate who miscued the ball from an inviting position inside the box with Phali, who looked to have had his angle at the near post covered, to beat.
Before the second half started, United players had a meeting on the pitch and within six minutes defender Morgan Gould opened the scoring as he rose above Cosmos defender Gladwin Shitolo and his goalkeeper Phali in the box to head home Klate's corner kick and take his league tally to six this season.
It could have been worse for Cosmos in the 65th minute when Klate received a delightful long pass from the midfield in the box from where he laid for oncoming Jabulani Maluleke who failed to connect properly with the ball under pressure from the opposition defender.
However, United got it right five minutes later when on-form Klate supplied a wonderful cross from the left flank that was blasted into the empty net by Mozambican international striker Monteiro.
United were not finished as experienced midfielder Brent Carelse hammered the final nail into the coffin of Cosmos with a thunderous free kick to give Phali no chance and register his first goal of the season.