The Real superstar’s Nou Camp double sunk bitter rivals Barca in front of Alex Ferguson and his No 2 Mike Phelan.

And it earned under-fire Real boss Jose Mourinho a Spanish Cup final spot.

Real and Ronaldo head to Old Trafford next week with their Champions League last-16 second-leg tie poised at 1-1.

And former Red Devils favourite Ronaldo, who was targeted by a home supporter’s laser pen, said: “This win gives us enormous confidence for the game against Manchester United.

“It was a great game and we played brilliantly. From the first to the last minute we were very serious, with a great attitude.

“We played better than Barcelona, to score three goals at the Nou Camp is extremely complicated.”

Rafael Varane added Madrid’s third — to clinch a 4-2 aggregate win — before Jordi Alba grabbed a late consolation for Barca.

Mourinho sent injured Real skipper Iker Casillas to speak in his place afterwards in a move of pure theatre given the well-publicised bust-ups between the two in the last 12 months.

And Casillas warned United Ronaldo will prove too hot to handle next Tuesday.

The Spanish No 1 said: “Cristiano is vital for us. Right now he’s in sensational form and gives us his maximum.

“He was absolutely brilliant tonight but so were the whole team. We have a 1-1 draw from the first leg against United and we have to score and keep a clean sheet.

“It will be difficult as they also know how to play and their ground is tough to play at.

“We have to transfer what we did here at the Nou Camp to Old Trafford.”

Real arrived at the Nou Camp chasing a goal after drawing the first leg 1-1 at the Bernabeu.

Ronaldo struck the opener from the spot on 13 minutes after Gerard Pique brought him down.

He added a second after 56 minutes to all but kill off the tie as it left Barca needing three to go through.

Varane headed Madrid’s third midway through the second half before Alba netted for Barca with a minute left.

It was the sixth successive El Clasico in which Ronaldo has scored and Casillas insisted the Spanish giants MUST make sure he signs a new deal to stay.

Casillas added: “Cristiano’s really showing it. He’s a very important player.

“All the players know he’s our player of reference. He’s already showed his level at the Clasicos in the past.

“As for his contract, it is a situation that the club and the player have to look at — but all of us want him to stay.

“The game against United will be difficult. The Champions League is more possible for us because of the difference in points in La Liga.”