With the scores deadlocked at 1-1, the Portugal star kicked out at defender Edimar after a tussle at the far post following a free kick.
Referee Alejandro Hernandez issued an immediate red card to Ronaldo - the fourth of his career in La Liga - and the Ballon d'Or winner took to Twitter after the game to accept he had only himself to blame for the incident.
"I apologise to everyone, and especially to Edimar, for my thoughtless actions during the game today," he said.
