WASHINGTON -- D.C. United maintained their mastery of the New York Red Bulls on Thursday night, securing the Atlantic Cup for the seventh time in the trophy's eight years of existence with a 2-0 win at a rain-soaked RFK Stadium.Though the visitors set after their I-95 rivals with energy and intensity, United's midfield was marginally superior on the evening and in the end New York had no answer for a well-crafted first-half goal from Santino Quaranta. Jaime Moreno sealed the result with a late penalty kick that runs his career scoring total to 126 goals.United jumped out to a strong start as Fred raced down the left flank in pursuit of Marc Burchís long ball in the second minute, the Brazilian's endline cross forcing Danleigh Borman to lump clear at the far post with Santino Quaranta lurking. Clyde Simms latched onto the loose ball and sent a long-range effort fizzing just wide of New York goalkeeper Jon Conway's right-hand post.Red Bulls playmaker Jorge Rojas soon carved out his own look at the United goal, surging forward to clip a low left-footer from 20 yards. D.C. 'keeper Josh Wicks was well positioned for the save but couldn't glove the slick ball cleanly, though with no white jerseys following the play he had ample time to clean up after his own mistake.Several hours' worth of steady precipitation had thoroughly soaked the field, the fans and just about everything else at RFK, creating treacherous footing for both teams. But the weather also brought unseasonably cool temperatures, a welcome change that prompted an end-to-end first half as both teams energetically chased the opening goal.Twenty minutes in, Chris Pontius fired a dipping shot just wide after a neat interchange among the United frontrunners, though Conway looked to have the angle covered regardless. In a tactical twist from D.C. coach Tom Soehn, Pontius had essentially switched spots with his fellow rookie Rodney Wallace for this match, occupying the left wing role as Wallace moved into central midfield for the first time this year.Two minutes later United alum Mike Petke reached Juan Pablo Angel's angled header in the D.C. box and sent an instinctive flick on target, but his effort lacked the pace required to beat Wicks.Simms and Rojas were waging a feisty battle in front of the D.C. defense and the United holding midfielder earned the game's first booking in the 27th minute from referee Terry Vaughn, who adjudged Simms to have caught Rojas on his follow-through as he knocked a loose ball back to Burch.In the 36th minute United seized the breakthrough they'd been hunting for on a clever move down the right channel. Luciano Emilio's flicked header at the edge of the Red Bulls box found Fred motoring into space behind the New York defense, and the Brazilian skipped an inviting endline cross into space at the near post. The feed was crisply dispatched by a late-arriving Quaranta, who outraced Jeremy Hall to notch his second goal of the season from five yards out.Borman was finding some joy along the Red Bulls left flank and he looked set to score when he floated into the D.C. box to meet Seth Stammler's angled cross some two minutes from halftime. But he got the ball stuck under his feet on the wet turf, allowing Wicks to advance and make a forceful claim that sent Borman sprawling. Both coaches made adjustments at the half. Soehn brought on playmaker Christian Gomez in place of N'Silu, while Red Bulls boss Juan Carlos Osorio gave rookie Nick Zimmerman - who had shown well in New York's 5-3 U.S. Open play-in loss at RFK last month - his MLS debut in relief of Carlos Mendes, as Osorio switched from a 3-5-2 to his more usual 4-4-2 system.Gomez made an immediate impact, sprinting at the heart of the Red Bulls defense and uncorking a wicked drive towards the lower corner of goal in the 49th minute, drawing a sharp parry from Conway. Emilio tracked down the rebound and sent in a cross that Gomez nodded just high of the target, the ball bouncing off the top of the crossbar and out.After misting in the first half, the rain resumed in earnest as the second stanza unfolded and while it did little to diminish the spirited chanting from United's supporters' groups, both squads found it increasingly difficult to link together cohesive play on the greasy turf. Emilio had been booked for a two-footed challenge on Goldthwaite in the 60th minute and Soehn withdrew the Brazilian striker for Jaime Moreno with an eye towards finishing the night with 11 men. But Emilio took exception to the move and angrily heaved a Gatorade bottle as he reached the United bench, drawing a red card from Vaughn that will sideline him for at least one match to come.His replacement, Moreno, boosted the home side's attack with his usual composure on the ball, though a second, clinching goal proved elusive. A nifty turn allowed Pontius to slip clear into the New York box in the 74th minute, but with the game on the line Conway came up big, moving off his line alertly to close down the rookie's angle as Pontius clanged his shot off the big netminder's face.At the other end, Zimmerman cut in from the right touchline and uncorked a well-aimed drive that forced Wicks to make an alert block at his right-hand post. On the ensuing corner kick, Angel rose above a crowd of bodies near the penalty spot but was unable to direct his header on target.Later, the Colombian did even better on a free kick just outside the United box, curling his shot over the wall but mere inches high of the target as the ball skimmed just over the bar.Angel and his mates continued to push for the leveler and went agonizingly close in the 86th minute as Dane Richards chased down Burch's misdirected header and scooped a clever pass over Bryan Namoff and right into the path of Angel, who had the goal at his mercy just 15 yards out. But Wicks produced a clutch save, dropping low to his right to palm Angel's one-timer away from the net and preserve the lead.D.C. finally iced the game on an injury-time penalty kick created by a swift counterattack from two veteran masters of the technique, Gomez and Moreno. Moreno took a loose ball deep in his own half and raced the other way, holding off Zimmerman for nearly 50 yards before playing a short pass into the path of Gomez, who advanced on Conway and cut past the diving 'keeper, who could do little to stop himself from clipping the Argentinean. Vaughn pointed to the spot and Moreno coolly dispatched the penalty to secure a 2-0 victory and another year of Atlantic Cup dominance for United.The Red Bulls must turn right around and face another Eastern Conference test, playing the New England Revolution on Sunday afternoon at Gillette Stadium. D.C. United have more than a week before their next game, remaining at home to take on the Chicago Fire on June 13.New York Red Bulls (2-8-3) vs. D.C. United (4-2-7) June 04, 2009 -- RFK Stadium Scoring Summary: DC -- Santino Quaranta 2 (Fred 3, Luciano Emilio 2) 36DC -- Jaime Moreno 4 (penalty kick) 93+New York Red Bulls -- Jon Conway, Carlos Mendes (Nick Zimmerman 46), Kevin Goldthwaite, Mike Petke, Danleigh Borman (John Wolyniec 79), Jeremy Hall, Albert Celades, Seth Stammler, Jorge Rojas, Juan Pablo Angel, Dane Richards,Substitutes Not Used: Danny Cepero, Juan Pietravallo, Luke Sassano, Khano Smith, Sinisa UbiparipovicD.C. United -- Josh Wicks, Bryan Namoff, Dejan Jakovic, Marc Burch, Chris Pontius, Fred, Clyde Simms, Rodney Wallace, Luciano Emilio (Jaime Moreno 63), Ange N'Silu (Christian Gomez 46), Santino Quaranta (Devon McTavish 88),Substitutes Not Used: Andrew Jacobson, Greg Janicki, Thabiso Khumalo, Milos KocicMisconduct Summary: DC -- Clyde Simms (caution; Reckless Tackle) 27DC -- Luciano Emilio (caution; Reckless Tackle) 60DC -- Luciano Emilio (ejection; Abusive Language) 64NY -- John Wolyniec (caution; Goalkeeper Interference) 94+Referee: Terry VaughnReferee's Assistants: C.J. Morgante; Corey Rockwell4th official: Andrew ChapinTime of game: 1:51Attendance: 11,226Weather: Rain -and- 61 degreesAll statistics contained in this boxscore are unofficial.