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.
The keeper came for a corner and dropped it, with the Mexico defender reacting fastest to fire home.
Real Salt Lake sit third in the Western Conference after their latest win, five points behind leaders Seattle Sounders.