Returning forward Ronaldo bagged two goals and Sergio Ramos the other, as the Portuguese superstar - currently serving a domestic ban - took his Champions League scoring tally to a record 107.
Speaking to reporters after the match, the 32-year-old said: "There's still a long way to go; let's go game by game. First we have the group stage then we can see. We of course want to win this tournament. The Champions League is Real Madrid's competition and we want to win it.
"I'm delighted to be back playing. This is a distinct competition and to start playing again and scoring goals is very important for me. I helped the side and feel good about that. It was a game we needed to win; we played at home and wanted to start the Champions League well.
"I think the side were good; we know we were taking on a defensive outfit. We could've scored more but in the end it was a good result and we've started off well and we're happy with that."
Ronaldo still has two games left to run on his five-match domestic ban for shoving a referee in the Supercopa de Espana victory over Barcelona last month.