The hosts were without a win since September 19 but it took them just five minutes to break through as they took advantage of poor defending from the visitors, Obafemi Martins sliding the ball across goal for Clint Dempsey to score from close range.
The early setback seemed to rattle Salt Lake, and Sounders doubled their advantage before the 10-minute mark thanks to a fine strike from Marco Pappa as the Guatemalan curled the ball inside the far post from 20 yards.
Dempsey and Andreas Ivanschitz had free kicks blocked as Sigi Schmid's side kept coming, and they put the result beyond doubt with less than a quarter of the match gone when Dempsey netted his second after Jeff Attinella had denied Martins in a one-on-one.
The visitors finally had their first efforts three minutes before the break when Juan Manuel Martinez and Javier Morales saw shots blocked as Sounders sat back, but by that point the damage had been done.
Luis Gil pulled a goal back from close range with 13 minutes remaining, but Seattle saw out the victory with little trouble to keep themselves in the running for MLS Cup glory.