Ruiz unleashed a left-footed shot from outside the box that sailed through traffic and beat Stefan Frei (three saves) to forge a tie.
Defender Justen Glad also scored in the 50th minute for Real Salt Lake (2-1-5, 11 points), who have recorded 10 goals in their last three matches (1-0-2).
Captain Nicolas Lodeiro scored on a penalty kick in the 29th minute and defender Yeimar Gomez added his first career MLS goal for the Sounders (4-1-3, 15 points), who have scored eight times during their last three matches (2-0-1).
The match was the first at home for Real Salt Lake since owner Dell Loy Hansen's controversial comments following the MLS player-led walkout and subsequent announcement to sell the team. Hansen also came under fire in a published report of his repeated use of racist language to and in front of team employees.
Alex Roldan made a slick move to create space in the corner before his cross found Gomez, whose header from the left side of the box beat Andrew Putna (zero saves) to give Seattle a 2-1 lead in the 69th minute.
Real Salt Lake forged a tie at 1 in the 50th minute after Albert Rusnak's corner kick found Glad, whose header handcuffed Frei at the goal line. The goal was Glad's first of this season and third of his career.
Seattle struck first as Lodeiro converted a penalty kick in the 29th minute after his left-footed shot found the vacated portion of the net. Lodeiro's goal was his second of the season for the Sounders, who received the opportunity as a result of Real Salt Lake's Aaron Herrera being issued a yellow card for a hand call in the penalty area.
Lodeiro also scored in the teams' last meeting, a 2-0 victory by Seattle in the 2019 Western Conference semifinals.