Toronto, longtime doormat of Major League Soccer, appeared to turn a corner after winning its first two matches of the season.
But Saborio put two past TFC goalkeeper Julio Cesar to see the Claret and Cobalt bring Ryan Nelsen's side back down to reality.
RSL went in front after 11 minutes when Doneil Henry brought Saborio down in the box, which allowed the Salt Lake striker to convert from the ensuing shot attempt.
The lead was doubled in the 28th minute when Luis Gil fired a shot that took a slight deflection on its way past Cesar.
Saborio then put the win on ice in the 55th minute by latching on to through ball and lobbing a shot past the on-rushing Cesar and into the back of the net.
Real Salt Lake, on eight points, is off to a great start under new head coach Jeff Cassar, going unbeaten through its first four matches of the year.
Toronto's first loss of the season leaves the Canadian side on six points.