The victory marked the third season in succession that Madrid have triumphed on the turf of their rivals, and Ronaldo says that the displays have been superior to their performances at the Santiago Bernabeu.
"It was a very good game, we played very well," Ronaldo told AS. "From the first minute to the last we were very focused, with a great attitude. We played better than Barca, scoring three goals in the Nou Camp is extremely difficult.
"Lately whenever we play here we do very well. We play better here than at home.
"We must continue with this confidence. Most of the players like to play here and things are going well for us."
Madrid will face either Atletico Madrid or Sevilla, who contest their second leg with the former leading 2-1 on Wednesday, in the final.