The home side were not finished, however, and made it four late on through Dani Carvajal.
The result at the Bernabeu moved Madrid above Barcelona into second position in the table, while Osasuna have dropped to 17th and remain just three points outside of the bottom three.
Here, Sports Mole dissects the 90 minutes of action between the two La Liga rivals.
On target: 10
On target: 0
Was the result fair?
In truth, it was just about the most one-sided 90 minutes of football imaginable at this level of competition. Los Blancos hardly got out of second gear for long spells of the first period, but entered the interval with a one-goal lead. The match was all but over as a contest when Ronaldo completed his brace in the early stages of the second period and Osasuna simply could not recover. When taking into account missed opportunities, especially for Ramos, who could have had a hat-trick this evening, Osasuna were extremely lucky just to concede the four on their visit to the Bernabeu.
Real Madrid's performance
With the second leg of their Champions League semi-final tie against Bayern Munich to come next week, head coach Carlo Ancelotti made a number of changes to his first XI. However, such is the strength of the Italian's squad that he was still able to field a team full of quality. It wasn't Madrid's best performance of the season, but they simply had far too much for an Osasuna team that lacked invention and a serious work-rate for long spells. Ronaldo was withdrawn shortly after scoring his second with a view to keeping the Portuguese fresh for the European clash next week. The likes of Nacho, Asier Illarramendi, Isco and Marcelo were handed valuable minutes, meanwhile, on a successful night for Ancelotti. Perhaps the only disappointment is that there were not more than four goals. The gap between the two teams this evening was just exceptional.
Granted, Osasuna would not have picked out this match as a must-win as they battle to avoid the drop this season. However, their overall performance this evening was extremely disappointing. They had a positive 15-minute spell either side of Madrid's first goal, but never really kicked on as Los Blancos took full control of proceedings. Oriol Riera - their leading scorer - has had an impressive season, but was too often left isolated in the final third as the Madrid back four were allowed to coast. Even when the score was just 1-0, Osasuna never offered the impression that they were capable of turning it around and failed to register a single shot on target. It was almost as if many of their players wanted the match out of the way as soon as possible. As it stands, they are just three points outside the drop zone with three games remaining.
Sports Mole's man of the match
Cristiano Ronaldo: Ronaldo's teammate Angel di Maria must be mentioned, with the Argentine's two assists in Madrid making him the leading player in La Liga for assists this season (14). However, it is difficult to look past Ronaldo for this particular award this evening. The Portuguese, who has only just returned from injury, might have played just 62 minutes, but he contributed to Madrid's victory with two stunning long-range efforts. The attacker's brace took him onto 30 league goals and 47 in total for the season.
Ramos's attacking play was rewarded in the second period when the Madrid centre-back headed a Di Maria cross into the back of the net from close range. However, the Spaniard should have had a hat-trick this evening. First, the defender headed a Ronaldo pass over the crossbar in the first period, before striking an effort straight into the arms of Osasuna goalkeeper Andres Fernandez after finding himself all alone inside the opposition's box. He got his goal, but it should have been a famous treble for the 28-year-old.
Incredibly, referee Fernando Teixeira failed to award a single yellow card this evening. Osasuna were not best pleased with Madrid's first, with Ronaldo seemingly standing in an offside position when he collected the ball, but the linesman's flag stayed down, which made it difficult for the referee to make that particular call. The Spaniard also had a couple of penalty shouts to assess, but made the correct calls in the capital. In truth, he was not seen for long spells, which is always a good sign for an official.
Real Madrid: Los Blancos travel to Germany for the second leg of their Champions League semi-final against Bayern Munich on Tuesday. The Spanish side hold a 1-0 advantage following the clash in Madrid last week.
Osasuna: Osasuna return to Pamplona next Saturday as they host Celta Vigo in the league.