The Portland Timbers spoiled the party for their archrival Seattle Sounders, winning 3-0 at Lumen Field on a day when the Sounders raised their CONCACAF Champions League title banner.
Jaroslaw Niezgoda scored in the first half, his fourth in the last four matches while midfielders and Santiago Moreno and Dairon Asprilla each scored in the final ten minutes.
Jackson Regan was sent off a minute into the second half, reducing the hosts to ten men. Seattle are winless in seven matches at home against their Cascadia Cup rivals in regular-season play.
Story of the match
The chippiness was evident early when Eryk Williamson picked up a yellow card for hauling down Raul Ruidiaz in the Portland half in the sixth minute.
Three minutes later, the Timbers registered the first shot of the match through Sebastian Blanco, but it was deflected and easily collected by Stefan Frei.
From a corner kick, Seattle tested Aljaz Ivacic as Nicolas Lodeiro saw his point-blank effort saved by the Portland goalkeeper. Claudio Bravo then cleared the subsequent header off the line.
On 24 minutes, the visitors were in front. After winning the ball back, Yimmi Chara found Blanco in space down the right. He sent it to the back post for an unmarked Niezgoda to finish.
Seven minutes from halftime, the Sounders' appeals for a penalty were waved away as Lodeiro went down from a challenge by Josecarlos van Rankin.
The match should have been level on the stroke of halftime, Ruidiaz' volley from a rebound in the penalty box going wide after hitting the post.
Regan had picked up a yellow card after elbowing Niezgoda and within a minute of the restart was sent off following after a dangerous challenge on Williamson that resulted in his second yellow.
Blanco then worked his way free, but Frei came up big to deny his shot from point-blank range.
Ten minutes from time, Portland were awarded a penalty. A shot by Moreno appeared to go out for a corner, but a check of VAR showed Nouhou had gotten a piece of the ball with his hand.
Moreno then stepped up to the spot and calmly beat Frei in the bottom corner to double the Timbers' advantage.
Asprilla then capped the scoring as he received a square ball from Niezgoda and finished off a lovely counterattack to put the icing on the cake for Portland.
Man of the match: Santiago Moreno
He had a superb game, providing a pair of assists to raise his team-leading total to seven and scored one that he so richly deserved for the performance he gave.