RSL (8-8-6, 30 points) snapped a two-match losing streak and won for the fourth straight game at home. The victory allowed Salt Lake to remain above the playoff line in the West, in seventh place.
Dallas (6-10-7, 25 points) has just one win in its past five games and had a four-match unbeaten road streak snapped. FCD slipped to 11th place in the West, five points in back of Real Salt Lake.
The teams tied 2-2 in North Texas in their first meeting of the season on May 22.
FC Dallas grabbed the advantage in the 19th minute when Franco Jara split two RSL defenders, took a pass from Jesus Ferreira in the center of the box and beat RSL goalkeeper Andrew Putna to the bottom left corner.
Real Salt Lake tied the match in the 42nd minute as Justen Glad made short work of a precise crossing pass by Aaron Herrera following a set piece situation. Glad's header from very close range to the bottom right corner that left FCD keeper Phelipe Megiolaro helpless.
RSL jumped to the lead in the 54th minute on a goal by Menendez.
Noah Powder's left-footed shot from outside the box glanced off FCD defender Emmanuel Twumasi and was batted down by Megiolaro. But it bounced right to the feet of Menendez, whose right-footed shot from the right side of the six-yard box was ripped into the center of the goal.
Rusnak added to RSL's advantage in the 72nd minute, strafing a right-footed shot off Megiolaro and into the goal after a crossing pass from the right side by Menendez.
Dallas clawed back to within a goal in the 80th minute when Ferreira took off with the ball down the right side, dribbled into the box and juked two RSL defenders to the ground before going one-on-one and beating Putna to the short side.