Atletico Madrid became outright leaders for the first time since their double winning season in 1996 earlier with a 4-0 win over Real Sociedad. (Agencies)
The draw moves Real level with Barcelona, who suffered a shock defeat at home to Valencia on Saturday, three points behind Atletico.
It could have been so much better for Madrid as after a difficult opening 45 minutes, Jese Rodriguez looked to have them on the road to a 11th consecutive victory when he prodded home Ronaldo's cross 25 minutes from time.
However, after Ibai Gomez had spectacularly equalised, Ronaldo was shown a soft red card for lashing out at Carlos Gurpegi.
And in the end Madrid were grateful to goalkeeper Diego Lopez for salvaging a point as he made lave saves from Gomez and Aritz Aduriz.
Carlo Ancelotti's men could have been in front after just 20 seconds as Ronaldo took advantage of a poor clearance by Gorka Iraizoz, but his effort flew inches wide.
Thereafter, it was Athletic who had the upper hand in the first-half and should have been in front when Aduriz shot wide when clean through on Diego Lopez.
Iker Muniain also passed up a great chance to open the scoring when he miscontrolled when unmarked inside the area.
However, Madrid responded after the break and Iraizoz was forced into two flying saves to deny Luka Modric and Karim Benzema.
The visitors did finally find a way through 25 minutes from time as Benzema fed Ronaldo on the left and his low cross was turned home on the stretch by Jese.
Real's lead lasted just nine minutes as Gomez made a stunning introduction as a substitute as with his second touch he fired an effort from 20 yards in off the inside of the post.
Madrid were then left to hold on for a point when Ronaldo saw red after a coming together with Gurpegi after having a penalty appeal turned down.
Gomez was denied a second by a brilliant save from Lopez, whilst the Madrid keeper also had to be alive to hold Aduriz's header as the spoils were shared.
Atletico Madrid became outright leaders for the first time since their double winning season in 1996 earlier with a 4-0 win over Real Sociedad.