Ronaldo latched on to a Karim Benzema pass in the 52nd minute and beat Gianluigi Buffon with a right-footed finish to level the scores at 1-1 after Arturo Vidal had blasted the Bianconeri in front from the penalty spot in the first half.
It was the Portuguese's eighth goal in four Group B games this term and his 14th in the Champions League this calendar year, a total which sees him surpass Messi's 13 strikes in 2012.
Ronaldo's goal was his 59th in the Champions League. The Portuguese now trails only Messi (63) and Raul (71). He also needs just one more strike to set a new group stage record currently shared with Hernan Crespo, Filippo Inzaghi and Ruud van Nistelrooy.
Messi, meanwhile, can add to his tally for Barca on Wednesday at home to AC Milan. The Argentine has hit seven goals in the Champions League in 2013, having been restricted by injury at the end of last season and also at the beginning of the current campaign.
