The victory - Joao Plata's opener added to by Chris Schuler's double, all inside the first 24 minutes - took RSL a point ahead of the Seattle Sounders and kept DC two points behind Eastern leaders Sporting Kansas City. It was also a historic night for Salt Lake keeper Nick Rimando, whose clean sheet against his former employers was his 113th in MLS and a league record.
FC Dallas are three points behind RSL after beating the Colorado Rapids 3-1. Again the damage was done early on, Matt Hedges scoring in the ninth minute and Michel Garbini adding a penalty two minutes later. Fabian Castillo made it 3-0 ten minutes after half-time and Gabriel Torres' late penalty was mere consolation for Colorado.
In the East, Toronto FC beat the Columbus Crew 3-2 and are third in the conference, seven points behind Kansas. They were twice pegged back after taking the lead, Junior Gilberto and Jonathan Osorio's goals cancelled out by Federico Higuain's penalty and Justin Meram's 81st-minute strike, which looked set to earn the Crew a point. Luke Moore had other ideas, though, the former Aston Villa and Swansea City striker heading in a corner to add to his two earlier assists.
The Philadelphia Union beat the Montreal Impact 2-1, Sebastien Le Toux's double proving enough despite Maxim Tissot's reply.