After reigning champions Barcelona were beaten by Real Valladolid, Carlo Ancelotti's side sit firmly in the driving seat following a routine home victory, with city rivals Atletico Madrid occupying second spot.
While Levante showed some of the defensive solidity that had helped them to an unbeaten run of eight league matches, Real's forward threat proved too strong.
Real's front three of Ronaldo, Karim Benzema and Gareth Bale all found the net during the international break and it was the former who broke the deadlock early on.
The Portugal star produced a well-executed header from a corner to hand Real the lead and played in Marcelo shortly after the interval, with the Brazilian registering his first goal of the season courtesy of a powerful right-footed finish.
Levante's cause was harmed when David Navarro was sent off just after the hour mark for a late tackle on Ronaldo, after which Nikolaos Karabelas put the ball into his own net as the hosts made it 16 straight wins at the Bernabeu in all competitions.
Ronaldo turned provider for the second, which saw Marcelo shimmy past Navarro, cut onto his right foot and fire past a helpess Navas to record his first league goal since January 2012.
Keylor was again called into action to deny Benzema before Levante were reduced to 10 men as a result of Navarro's late challenge from behind on Ronaldo.
Karabelas inadvertently swept Marcelo's cross into his own net to put the result beyond any doubt nine minutes from time.
