Valencia and Real Madrid each missed the chance to close the gap on leaders Barcelona after a goalless draw at the Mestalla.
Both sides had chances in the late match in Spain, but the most contentious moment came just minutes from the end.
Ronaldo, who started on the substitutes' bench for the visitors, came on to earn a controversial penalty in the dying stages when he fell over the legs of Valencia goalkeeper Santiago Canizares.
The big Brazilian stepped up to take the spot kick, but Canizares easily stopped it to earn a deserved point for Los Che.
The result takes Valencia above Real to second in the table, with both clubs nine points adrift of leaders Barca.
Espanyol pulled away from relegation trouble with a 2-0 home win over Celta Vigo.
Raul Tamudo gave the Barcelona club the lead on 13 minutes at the Montjuic before Espanyol were reduced to ten men.
Armando Sa was sent off on 27 minutes for committing a professional foul, but that did not stop the Brazilian Fredson from doubling Espanyol's lead on 38 minutes.
The result takes Espanyol seven points clear of the bottom three in the Primera Liga table, while Celta missed the chance to move into the top four following defeat on Saturday.
A second-half header from Gaizka Garitano gave Real Sociedad a vital 1-0 win at Deportivo La Coruna.
The Basque club had slipped dangerously close to the relegation zone in La Primera, but the former Eibar player's winning goal meant a crucial three points were taken from Saturday's trip to the Riazor.