Keylor Navas made his first appearance of the season in Madrid’s goal after an injury-hit summer and start to the campaign as three other changes from the weekend’s 1-1 draw at Las Palmas saw Danilo, James Rodriguez and Karim Benzema all enter the fray.
In a pulsating match, packed with quality and chances, Ronaldo needed just a couple of minutes to force Roman Burki into a save from his free kick, but the No 7 blocked a set-piece at the other end with his arm, which Mark Clattenburg ignored.
Staying in Madrid’s box, Dani Carvajal’s backpass provoked an under-pressure Navas into a rushed clearance and Ousmane Dembele fired a shot just over.
Dembele paid the price for his selfishness moments later as Madrid broke back at the speed of light, Gareth Bale back-heeling in the penalty area for Ronaldo, who smashed a finish past Burki from close range.
The Frenchman pressed for the equaliser when he came inside from the right again, running onto Pierre-Emerick Aubameyang's layoff, and he shifted past Danilo before his shot deflected inches over the bar.