Playing against Manchester United where he grew into one of the world's top players for the first time since leaving in 2009, Ronaldo was the driving force for his side in the 1-1 draw that left the Champions League last-16 tie finely balanced.
Most of the pre-match hype revolved around him and while his performance did not disappoint, United's defenders can look back on their night's work in Madrid with much satisfaction.
Ronaldo prowled the pitch looking for opportunities to strike and although he had 10 efforts on goal, only once did he pierce United's defences.
Considering his record since joining Madrid, 183 goals in 180 matches after Wednesday, United secretly feared that he could have taken the tie beyond them, yet left with minimal damage and with the tie wide open for the Old Trafford return.
With all eyes on Ronaldo, he produced a tireless forward's display, spending most of his time around United's area and only occasionally indulging in the party tricks that used to drive Premier League defenders, and occasionally his own team mates, to distraction.
His goal, after 30 minutes, was one any of the great strikers that have graced the competition would have been proud of. When Angel di Maria's cross came over, Ronaldo rose high and hung in the air before flexing his neck muscles and propelling the ball past David de Gea.
A fine goal and he also showed class with his restrained celebration, a mark of respect for the fans that once used to sing his name on the Stretford End.
"What a header, you can't stop that," Ferguson, who moulded Ronaldo from a spindly over-elaborate winger into one of the world's most lethal forwards during six years at Old Trafford, told Sky Sports.
"The leap, the spring the way he held himself in the air. What a header."
Ronaldo should have scored from an almost identical position just before half-time but mistimed his header and he also went close on a couple of occasions before fizzing a long-range dipping shot on to the roof of the net.
Overall it was honours even on what Ferguson said was a difficult night for Ronaldo.
"I think we did well [in containing him]," Ferguson said. "I think it was difficult for Cristiano playing against us, his old team. There are a lot of emotions attached because he spent six great years with us.
"But he is still a big threat for them. When he gets the ball you are praying more than anything."
At the final whistle, Ronaldo spoke with several of his old team-mates who know that the job is only half done.
The 28-year-old will already be scheming for the second leg.
"They are a very strong team defensively," Ronaldo said.
"I think we played better and deserved to score more goals. We will have chances to score in the second leg, we always try to have the initiative and we will try to win in Old Trafford."
