Published: 2017-09-14 04:22:32 BdST
Ronaldo has been banned from domestic football since August for pushing a referee and only needed 12 minutes to get back amongst the goals in the competition where he is the all-time top scorer, meeting Gareth Bale's low cross to arrow home.
Captain Sergio Ramos rubber-stamped what was a routine victory for Madrid over the Cypriot champions with a scrappy overhead kick in the 61st minute.
Ronaldo was denied another penalty and a potential hat-trick when he was tripped in the area but his appeals went unnoticed, while late in the game he had a goal chalked off for a clear offside.
Ronaldo also strayed offside in injury time as he sent the ball across to Borja Mayoral, whose tap in was also ruled out.
The Portuguese still has one game left to serve of his five-game domestic ban and will miss Sunday's trip to Real Sociedad.
Madrid's opening goal came through a well worked break started by the sparkling Isco, who danced his way past his opponents to work the ball to Bale, who in turn found Ronaldo.
Bale has been much maligned in Spain recently for his timid performances this season but was involved in all of Real's goals, flicking the ball into the air and off the shoulder of Lago, who was in disbelief when the penalty was awarded.
"Cristiano scores so many goals and we really noticed his presence tonight, and I hope he keeps up this run," Ramos told reporters.
"His quality is unquestionable and Madrid are going to benefit from his return."