"I believe we played with a lot of heart tonight," Union team manager Peter Nowak said.
"I told the guys that I'm proud of their effort tonight. The last game [a 3-1 loss to FC Dallas] wasn't our best game . . . [but] we came back strong, and the mentality is getting better."
The Union next play the Colorado Rapids on Saturday at home.
Goalie Brad Knighton served his one-game suspension Wednesday after he was issued a red card against FC Dallas. He was replaced by Chris Seitz, the only goalkeeper in the league without a shutout.
But even with Real Salt Lake's leading scorer, Alvaro Saborio, out on duty with the Costa Rican national team, it was a tough challenge for Seitz, who finished with four saves but allowed a pivotal goal.
After the Union's Sebastien Le Toux fed Danny Mwanga for the opening goal in the eighth minute, Real Salt Lake (10-4-6) countered.
Fabian Espindola caught a cross from Tony Beltran, and netted the goal from about 5 yards out, helping Real Salt Lake cap a two-match road trip with ties.
"Yeah, obviously, we had a little bit of a letdown in the first half on one play, really," said Seitz, who was playing against his former team.
"That was their best chance of the game, and they capitalized. But for us, we need to take away that we created chances. So we have until Saturday to work on it and hopefully take a little bit of our style of play here and put it against Colorado."
The Union (4-10-4) survived some rough play, including four consecutive yellow cards issued to Real Salt Lake, three coming in the second half. The Union finished with two - one coming in the second minute; the other delivered in stoppage time for unsporting behavior.
The first-half play of the Union offered their fans cause for optimism, especially when Le Toux, the club leader in goals and assists this season, connected with Mwanga, second on the team in scoring, for his sixth goal this year.
With that, the Union can at least take solace in improving against Real Salt Lake. In their first meeting this season on May 8, the Union lost on the road, 3-0.
"I was very impressed with their team," Real Salt lake coach Jason Kreis said of the Union. "I have been since the beginning of the year."
Contact staff writer Mario Aguirre at 215-854-4550 or firstname.lastname@example.org.