Juventus coach Massimiliano Allegri insisted it shouldn't have been a red card, and lamented the fact that video technology has yet to be introduced into the Champions League, as it has been in Serie A. VAR was also used at the World Cup in Russian Federation this year.
While it was not the first time Ronaldo has seen red - it was his 11th career sending off - it was his first in the Champions League and the controversial nature of the card sparked fervent debate on social media.
It was his first red card in 154 Champions League games, and the decision means he is set to miss a return to Old Trafford when Juventus plays Manchester United next month.
He has received an automatic one-match ban which can not be appealed.
Ronaldo's European debut in Juventus colours ended prematurely against Valencia, when he received his marching orders after just 29 minutes.
The Portuguese player then made contact with Murillo's head while urging him to get up. Never write off Juventus Juventus have won Serie A seven years in a row and they used all their experience to silence the raucous Valencia fans and close out the win.
He is the Champions League's record scorer with 120 goals and led Madrid to the title the past three years - and four times in the past five.
Trump’s trade war still doesn’t scare China
The latest United States duties spared smart watches from Apple and Fitbit and other consumer products such as baby auto seats. USA stock markets opened higher and the Nasdaq index was up 1 over 1 percent by mid-morning.
Following the match, Mariano, who returned to Madrid in the summer window after the club bought him back following a single season with Lyon in 2017-18, said he was thrilled to open his UCL account for Real.
Burnely said the man with the whistle should have taken his time with making the decision and should have given the incident another look on VAR.
However, manager Julen Lopetegui preferred to talk about the team as a whole rather than individual performances from his two in-form stars following the match.
Former England defender Rio Ferdniand expressed disbelief over the ruling on Twitter, urging Juventus and Ronaldo to appeal the straight red card.
"It is very disappointing, we nearly lost because of that and we will be without Ronaldo for the next (game)".
Juventus host Young Boys next in the competition before two straight games against United, with the first match at Old Trafford on October 23. "We conceded many counter-attacks and at this level you get punished", said City assistant coach Mikel Arteta, who was filling in for Guardiola.