Jose Mari's early strike gave visitors Colorado the lead but they capitulated before half-time as Real extended their unbeaten streak at home to eight matches.
In stark contrast, the Rapids are now without a win in nine – eight of which have been losses.
Mari's stunning effort gave them early hope, though, as he slotted a 25-yard left-footed effort into the bottom-right corner in the 21st minute.
Joao Plata levelled proceedings 11 minutes later, running onto Ned Grabavoy's back heel before firing into the top-right corner.
Plata's 32nd-minute goal triggered a Real Salt Lake hot streak, and in the next minute, Javier Morales' corner snuck in at the near post.
Christopher Schuler added a third in the 37th minute before Colorado goalkeeper Joe Nasco inadvertently turned into his own net on the stroke of half-time after Plata's shot was heading wide.
Carlos Salcedo ended the rout just after the hour-mark as Nasco's poor night continued.
