The Portugal international was given his marching orders in the Mestalla for clashing with Colombian defender Jeison Murillo.
Ronaldo broke down in tears after German referee Felix Brych decided to send him off 27 minutes into his first Champions League game for the Italian champions.
After appearing not to have seen the incident, Brych consulted with his assistant behind the goal before showing the 33-year-old a straight red.
And he was clearly distraught as he left the pitch, still shaking his head.
Despite losing their club-record signing, Max Allegri’s team managed to win the game 2-0, with Miralem Pjanic netting twice from the spot.
Although it was the eleventh red card of his career, Ronaldo had never been sent off in 154 appearances within Europe's elite club competition.
And Can had his say after he was shown the incident after the game - and the 24-year-old was not sitting on the fence regarding the issue.
"That's supposed to be a red!?" he exclaimed when shown a video of the action by DAZN.
"I just heard that he said it was because of hair pulling. We're not women, we’re playing football.
"If you're giving that as a red card, you can be sent off for any foul. One hundred per cent, that is not a red card."