Nine players were cautioned and 39 fouls committed as RSL (4-13-6) battled back from a 1-0 deficit. Goalkeepers Nick Rimando (ex-United) and Troy Perkins each saved a penalty kick, off the feet of, respectively, Gomez and Alecko Eskandarian (also ex-United).
Gomez's failure illustrates that penalty kicks, which are usually taken by Moreno and make up a substantial chunk of his league-record 110 goals, aren't necessarily gimmees.
Fred, Clyde Simms and Greg Vanney sat on the bench at kickoff in favor of Guy-Roland Kpene, Brian Carroll and Bobby Boswell. RSL coach Jason Kreis ignored sentimentality and left defender Eddie Pope, being honored by D.C. for his seven years of service, on the bench. For the whole game.
Both United goals were created by superb crosses to the back post, where RSL's poor marking has been a problem for much of this season.
Gomez curled a ball that Emilio nodded home for his league-best 19th goal.
After Kyle Beckerman had drilled a low, 25-yard equalizer past Perkins, Gomez got on the other end of a Fred serve - of a ball backheeled to him by Bobby Boswell -- to head home the winner with 17 minutes left.
Referee Jorge Gonzalez whistled his first penalty minutes into the second half when Jean-Martial Kipre tripped Josh Gros. Rimando dove to his left to repel Gomez's rather tame effort.
For spot kick No. 2, Gonzalez ruled that Devon McTavish had fouled Carey Talley during a wrestling match as Perkins collected a harmless free kick, despite the fact McTavish wound up on the ground.
McTavish had already been cautioned, yet Gonzalez ruled a PK to be sufficient punishment, and Perkins slapped away Eskandarian's well-hit but poorly-angled penalty.
Sept. 12 in Washington, D.C.
D.C. United 2 Real Salt Lake 1. Goals: Emilio (Gomez) 16, Gomez (Fred, Boswell) 73; Beckerman (Wingert) 32.
D.C. United - Perkins, Namoff, Boswell, McTavish, Burch, Olsen (Simms, 80), Carroll, Gomez, Gros, Emilio, Kpene (Fred, 46).
Real Salt Lake - Rimando, Kipre (Lancos, 61), Kotschau, Mantilla, Wingert, Morales, Beckerman, Talley, Espindola (Findley, 72), Brown (Williams, 75), Eskandarian.
Yellow Cards: D.C. United - Olsen 39, McTavish 57, Gomez 73, Fred 82; Real Salt Lake - Kotschau 18, Eskandarian 28, Beckerman 49, Mantilla 88.
Referee: Jorge Gonzalez.