The Portuguese forward netted his 44th goal of the season against the Basque club on Saturday, meaning he has now reached a century in the Spanish top flight.
The attacker bagged his century for the Blancos in just his 92nd appearance for the club after scoring the second goal against Philippe Montanier's outfit at the Santiago Bernabeu.
His feat means he has now surpassed Ferenc Puskas' record of accumulating a century of La Liga strikes for Real Madrid in 115 matches.
The former Manchester United star had previously scored his 100th Real Madrid goal in the Champions League group stage against Olympique Lyonnais this season.
Real Madrid reopened a six-point gap on Barcelona with victory against Real Sociedad.
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