The Portuguese star expects a warm welcome at Old Trafford, but he admits he would love to score against former team. Ronaldo also scored in the first leg to give Real Madrid a draw against United after Danny Welbeck put the visitors in front with a header after just 20 minutes of playing time.
Ronaldo admitted he would love to score against his former team but isn't sure how he would celebrate the goal.
"It would be a beautiful sensation," he told reporters. "If I score against them, it would be spectacular.
"I can't say how I'd celebrate - it would be something spontaneous - but I'd love to be in that situation."
The 28-year-old also spoke how he expects a warm welcome after winning three Premier League titles and lifting the Champions League once during a six-year spell in the north west of England.
"I'm sure they will receive me well," said Ronaldo, who is the European competition's current joint-top scorer with seven goals.
"After the years I spent there and the friendships I have, I'm sure it's one of the places where they'll applaud me most. It was a beautiful time."