Alvaro Saborio got RSL's first goal in the 14th minute, Findley made it 2-0 in the 79th minute and Gonzalez notched his first goal of the season in stoppage time to cap the one-sided victory.
Salt Lake (10-4-4) has lost once in 13 games.
United (3-12-3) got its best chance at the 30-minute mark when Branko Boskovic chipped the ball over the head of goalkeeper Nick Rimando but it sailed narrowly over the crossbar.
Couple calls 9-1-1 over missing hash browns; assault McDonanld's employees
Ohio crash that killed two caught on camera [VIDEO]