Felix Brych showed the veteran a red card for an incident involving Jeison Murillo, although the Italian coach didn't want to focus on the perceived injustice the Bianconeri felt.
Just a few seconds later and the decision was taken to send off Ronaldo, giving him the first Champions League red card of his career in the process.
The 33-year-old is now likely to receive a two-match ban. After Murillo went down inside the area, the Portugal forward gestured for his opponent to get up, then put his hand on the Valencia defender's head and appeared to tug his hair.
His first real impression, however, was not what anyone in the Mestalla could have imagined though as he was sent off for the first time in the Champions League in his 154th appearance.
Down to 10 men and with a 2-0 lead, Juventus had no desire to add to their advantage and were focused on strangling any threat of Valencia clawing their way back into the game.
Pjanic converted spot-kicks either side of the break, while Valencia's Dani Parejo saw his penalty saved by Wojciech Szczesny in stoppage time.
Bayern beat Benfica 2-0 in the other game in the group, Robert Lewandowski and Renato Sanches getting the goals.
The Red Devils defeated the whipping team of the group Young Boys 3-0 at the Stade de Suisse Wankdorf.
The defending European champion Real Madrid got off to a winning start with a comfortable 3-0 victory over Roma, the goals coming from Isco, Gareth Bale and Mariano Diaz.