The result is seen in many quarters as the perfect vengeance for the Los Blancos for their Champions League semifinal exit last season over two legs against Dortmund. (JPN/Agencies)
Madrid flew out of the traps and were ahead within three minutes when Welsh wizard Bale poked home from Dani Carvajal's pass.
Isco doubled Madrid's lead after 27 minutes as his low shot from the edge of the area curled into the bottom corner.
Ronaldo then scored his 14th Champions League goal of the campaign to match the competition's record mark for goals in a season set by Lionel Messi two years ago.
However, Madrid's night was soured somewhat as Ronaldo had to be substituted late on due to what appeared to be a minor knee injury.
Madrid had also suffered a disruption just before the game as Angel di Maria was ruled out with gastroenteritis, but they didn't miss a beat without the Argentine as his replacement Isco pulled the strings in midfield and they started with great intensity.
Bale opened the scoring with his 17th goal of the season as he controlled Carvajal's low centre before finishing first time.
Dortmund goalkeeper Roman Weidenfeller then had to make two brilliant saves from a free-kick each from Ronaldo and Bale.
However, there was nothing the German international could do to prevent Isco's precise low effort finding its way into his bottom right-hand corner.
Madrid are now firm favourites to proceed to their fourth Champions League semifinal in as many years with a strong lead to take to Germany. Dortmund’s failure to score an away goal would also favour the Spanish giants.
The result is seen in many quarters as the perfect vengeance for the Los Blancos for their Champions League semifinal exit last season over two legs against Dortmund.