United marked their 150th UEFA Champions League game with a narrow win in the second leg becoming the first English side to beat the Portuguese club on home soil.
Ronaldo's rocket shot in the first half was enough to secure passage through to the semi-finals where Sir Alex Ferguson's side will meet Arsenal.
Reflecting on a testing spell for the Red Devils, the United star believes Wednesday's result will be a timely confidence boost.
"This will give us confidence," he told Sky Sports. "The last five games we didn't play great and I hope this will change that."
Describing his goal, the Portuguese forward said: "When Anderson gave me the ball I think straight away to turn and shoot in the goal and I score a fantastic goal.
"It is the best I have scored.
"It was a fantastic strike and I can't wait to see it again on DVD. I am very happy with it."
Conceding that the semi-final against Arsenal will be tough, Ronaldo admitted that the prospect of competing against another English side in Europe is an exciting one.
"It's a fantastic thing," he said of the tie. "Arsenal play fantastic football.
"It will be a tight game. We know each other and I hope to win the tie and go to the final."