Rimando produced six saves, three of which were brilliant reflex reactions, to what appeared certain goals and overcame a stray elbow from a collision that left him with a black eye in the first leg of the semi-final, played in front of more than 34,000 screaming and singing Seattle fans.
The result gives Real Salt Lake the edge heading home for the second leg on November 8 in Utah.
"We left everything out on the field today but we didn't get the result. We didn't score that's the only thing," Seattle goalkeeper Michael Gspurning said.
"Rimando came up with some huge saves and it makes it a little bit difficult for us now.
"We still have chances but Salt Lake is now favourite but we're not afraid to go there next Thursday.
"It's all or nothing next game. Don't write us off, we're still in the game and we will prepare and give 100 per cent."
Seattle's Jeff Parke and Brad Evans and Salt Lake's Kyle Beckerman and Javier Morales will take yellow cards into the second leg after being booked.