The Portuguese has netted just twice in the European competition this term and those came in Los Blancos' first two games in the group stages - at home to his old club Sporting CP and away to Borussia Dortmund.
The four-time Ballon d'or winner netted a fantastic free-kick as Madrid came from behind to beat Sporting 2-1 at the Santiago Bernabeu and then opened the scoring for Zinedine Zidane's side in Dortmund after 17 minutes in a 2-2 draw on September 27.
Ahead of the last-16 Champions League tie against Napoli on Wednesday, Ronaldo, who was 32 earlier this month, failed to add to that tally in the games home and away to Legia Warsaw, the trip to Lisbon and the meeting with BVB at the Bernabeu, becoming his longest stretch without scoring for Madrid in the continental competition, in which he has netted 80 in 81 games for Los Blancos.
The Portuguese has scored 34 in 38 fixtures for Real in knockout games in the competition, but he was unable to build on that when the reigning champions took on Napoli on Wednesday. While he got an assist for Toni Kroos in a strong 3-1 win, he was unable to bring an end to his dry spell which now stands at 523 minutes.
He will get the chance to get back to scoring ways when Madrid visit Maurizio Sarri's men for the return fixture on 7 March.