Ronaldo was then clearly annoyed by Murillo's play-acting and placed a hand on the defender's head.
Ronaldo was dismissed after a clash with Jeison Murillo was spotted by the assistant referee and communicated to German referee Felix Brych, who drew a red card from his top pocket.
The Portugal captain looked baffled and kept protesting his innocence, briefly laying on the ground to express his disbelief.
The straight red means Ronaldo would miss Juventus' trip to Manchester United, where he spent six seasons from 2003 to 2009 and blossomed into one of the world's best players, on Matchday 3 on October 23. The Italian club could appeal the red card decision.
It was Ronaldo's first red card in Europe's elite club competition in his 154th game.
Here are three thoughts from Wednesday's action in the Champions League.
However, the Portugal worldwide turned things around when he scored a brace in his side's 3-0 win over Sassuolo at the weekend.
Despite their numerical disadvantage, Juve took the lead through Miralem Pjanic on the stroke of half time.
Captain Paul Pogba produced an outstanding performance garnished by two goals to help Manchester United to a resounding 3-0 win at Swiss debutants Young Boys.
City, the bookmakers' favourites for the title this season, suffered a nightmare first half against an enterprising Lyon, with Maxwel Cornet sweeping in after a mistake by Fabian Delph, and Nabil Fekir drilling home before half-time.
Five-time champions Bayern Munich got their Group E campaign off to a solid start as Niko Kovac's men eased to a 2-0 triumph against Benfica in Lisbon.
Jesus wept. Is this really what the Champions League has come to?