Ronaldo was slapped with a five-game ban for pushing the referee after he was sent-off in the first leg, but his replacement Marco Asensio enhanced his reputation as one of world football's rising stars as he smashed Madrid into the lead after just four minutes.Karim Benzema then deservedly doubled Real's lead before half-time.
Barca responded with a more spirited second-half showing and were unfortunate not to at least pull a goal back as Lionel Messi and Luis Suarez hit the woodwork. Victory continues Madrid's run of success under Zinedine Zidane with the European champions now having lifted seven trophies in the 20 months since the Frenchman took charge.
Zidane even had the luxury of leaving first team regulars Gareth Bale, Isco and Casemiro on the bench as Real's strength in depth was demonstrated in a dominant first 45 minutes.
Asensio had already shown the threat he poses with a dangerous run and cross that saw Luka Modric's goalbound effort blocked by Samuel Umtiti before he found the net himself.
Just as in the first leg, the 21-year-old sent an unstoppable left-footed shot past Marc-Andre ter Stegen into the top corner from outside the box.
Worst possible start
Barcelona boss Ernesto Valverde has suffered the worst possible start to his reign with back-to-back defeats against the Catalans fiercest rivals and the visitors only briefly threatened to mount a comeback after conceding. Suarez volleyed over before Keylor Navas rushed from his goal to block from Messi.
However, shorn of Neymar after his world record breaking transfer to Paris Saint-Germain and injured captain Andres Iniesta, Barca's star front two lacked the service needed to make a meaningful impact.
Indeed, the scoreline could have been a lot more embarrassing for Barca as Marcelo dragged wide before Lucas Vazquez hit the post with a glorious chance.
The hosts finally doubled their lead six minutes before the break when Benzema nipped in front of Umtiti and slotted past Ter Stegen.
An 11:00 pm kick-off time meant half-time saw Wednesday turn to Thursday and Barca did at least salvage some pride in the early morning with an improved second-half display.
Messi was desperately unlucky not to net a consolation goal as he hit the underside of the bar from a narrow angle.
The visitors' night was summed up when Suarez headed against the post with the goal gaping after Navas had parried Messi's driven shot into his path.
And there could be even worse news to come for Barca as Suarez ended the game visibly suffering from a knee injury just four days ahead of their La Liga opener against Real Betis on Sunday.