He then smashed in an exceedingly first-time shot from Gonzalo Higuain's through ball before Leonardo Bonucci headed home to create it 3-0 before the break.
Ronaldo virtually grabbed his 1st Serie A hat-trick as he hit the post, before Ignacio Pussetto's late consolation.
Juve keeper Gianluigi Buffon created his 646th Serie A look, one wanting Paolo Maldini's uncomparable record.
It was Buffon's 700th league look together with Serie B and the French top flight.
Inter Milan can return to the top if they avoid defeat at Fiorentina.
