Ronaldo scored both goals, the first set up by Gareth Bale, as the Champions League winners started the new season with more silverware.
The crowd of approx 31,000 was a record for the newly extended Cardiff City Stadium and a record crowd for a one-off UEFA Super Cup match.
The event appears to have been a massive success and will have boosted Cardiff's hope of hosting more prestigious European events in future.
Real Madrid: Casillas 6.5, Carvajal 6, Pepe 6.5, Sergio Ramos 7, Fabio Coentrao 7 (Marcelo 84), Kroos 6.5, Rodriguez 6 (Isco 72 6), Modric 7 (Illarramendi 86), Bale 6.5, Benzema 7, Ronaldo 8.
Subs not used: Navas, Varane, Arbeloa, Di Maria.
Goals: Ronaldo 30, 49.
Booked: Carvajal, Kroos.
Sevilla: Beto 6, Coke 6.5 (Diogo Figueiras 84), Pareja 6, Fazio 6.5, Fernando Navarro 6, Alex Vidal 6 (Aspas 66 6.5), Krychowiak 6, Carrico 6.5, Vitolo 6, Suarez 6.5 (Reyes 78), Bacca 6.5.
Subs not used: Barbosa, Jairo, Iborra, Luismi.
Booked: Navarro, Vitolo.
Referee: Mark Clattenburg (England)
Attendance: 31,000
Match report from Sporting Life
The former Manchester United star struck in each half to secure a 2-0 win and underline Madrid's dominance of a game they controlled throughout.
The Spanish giants thrilled a capacity 33,500 crowd at Cardiff City Stadium with their all-singing, all-dancing game, and Sevilla's players were often reduced to a spectating role.
Bale, who joined Real from Tottenham in a world record £86million deal last summer, also stamped his class on proceedings, delivering a precision cross from which Ronaldo scored his opener.
And when he pounced again early in the second period, there was no way back for Europa League title holders Sevilla as the 2014 Champions League winners showcased their enviable quality.
Real boss Carlo Ancelotti paraded his awe-inspiring wealth of playing talent, with major summer signings James Rodriguez and Toni Kroos joining Bale and Ronaldo in a team captained by goalkeeper Iker Casillas.
James and Kroos both had their moments, with the electric speed of Colombia international James' pass a regular highlight, while Bale's former Spurs colleague Luka Modric worked tirelessly in midfield.
Although the Spanish domestic season does not start for almost another fortnight, Real already look in ominous form, suggesting they will not only challenge for another European crown but also seriously threaten Atletico Madrid's reign as La Liga champions.
Pre-match talk about the Sevilla side revolved around a player not involved - left-back Alberto Moreno - who is thought to be on the verge of joining Liverpool, with Sevilla manager Unai Emery seemingly resigned to that outcome.
Real predictably monopolised possession in the early stages, but Bale's first involvement almost saw him put through by Ronaldo. He appeared to be brought down on the edge of Sevilla's penalty area, yet referee Mark Clattenburg waved play on.
Bale then saw a shot deflected narrowly wide as pressure began to mount, and when Ronaldo was sent crashing to the turf, Clattenburg this time gave a free-kick that Ronaldo dipped just over the bar.
Casillas was not called into action until the 20th minute, and he had to be alert at his near post to block a Vitolo shot as Sevilla displayed a counter-attacking hunger after being penned deep inside their own half.
Ronaldo should have put Real ahead following Karim Benzema's excellent approach work, yet having eased past two Sevilla defenders he shot straight at advancing Sevilla goalkeeper Beto.
It was a let-off for the underdogs, but Ronaldo was not to be denied 15 minutes before the break, finishing from close range for his 17th goal in 10 appearances against Sevilla after Bale's inch-perfect cross created a gilt-edged opening.
Sevilla could have few complaints, having played second fiddle for long periods as Real's masterful exhibition of passing meant they enjoyed prolonged periods of control.
Casillas was pressed into his second save of the game as half-time approached, deflecting a Daniel Carrico effort high and wide, but Real had no further scares in securing a 1-0 interval advantage.
And Ronaldo stamped a defnitive mark on proceedings just four minutes after the break when he rifled a powerful left-footed shot into the corner of Beto's net to double Real's lead.
Despite having effectively wrapped the game up, Real showed no intent to take their foot off the accelerator and Ancelotti will have been thrilled with their desire during the closing stages of a one-sided encounter.
James went desperately close to making it 3-0, but his powerful drive was superbly turned around the post by Beto, then Modric was narrowly off-target with a shot from outside the box.
Emery sent on former Arsenal player Jose Antonio Reyes among his late substitutions, but Real were already in cruise control and they comfortably closed the game out as they added more silverware to a bulging Bernabeu trophy cabinet.