While Buffon starred in goal for Juventus, saving a penalty and making two remarkable saves in a 1-0 win at Lyon, it was a frustrating night for record-chasing Ronaldo in the Champions League.
The Real Madrid forward needed only two goals to become the first player to score 100 career goals in European club competitions. But he could not muster even one for the holders in a 5-1 rout of Polish strugglers Legia Warsaw - which had lost five of its past seven matches.
Madrid has scored 11 times in its past two games, but only one of those has been from the usually prolific Ronaldo. He has made an uncharacteristically quiet start to the season for Madrid with four goals in eight games so far - very low by his own lofty standards.
Madrid's goals came from Wales forward Gareth Bale, an own-goal by Tomasz Jodlowiec, and further strikes by Marco Asensio, Lucas Vazquez and Alvaro Morata, sealing an emphatic victory in Group F.
Madrid is level on seven points with Borussia Dortmund, but the German side leads on goal difference after winning 2-1 at Sporting Lisbon.
Prolific striker Pierre-Emerick Aubameyang - with his ninth goal in nine games - and Julian Weigl scored in the first half for Dortmund. Midfielder Bruno Cesar pulled one back midway through the second half after an indirect free kick was awarded near the penalty spot.
Colombia midfielder Juan Cuadrado scored the winner for Juventus in the 76th minute with a brilliant angled strike, keeping the Turin team top of Group H.
Here's a look at what else happened in the Champions League on Tuesday:
Tottenham striker Son Heung-min came back to his old club Bayer Leverkusen, but the German side did most of the attacking in a 0-0 draw that suited Monaco perfectly.
Monaco came from behind to salvage a 1-1 draw at CSKA Moscow and tops Group E with five points, one point ahead of Tottenham and two clear of Leverkusen.
Although Tottenham had chances in the first half, with Dutch striker Vincent Janssen hitting the crossbar, Leverkusen dominated after the break.
Spurs goalkeeper Hugo Lloris did brilliantly to scoop the ball away on the line after an effort by Javier ''Chicharito'' Hernandez - with goal-line technology showing that it hadn't fully crossed the line.
So much for not celebrating against your former club.
CSKA Moscow striker Lacina Traore could barely contain his delight after scoring against Monaco - the club loaning him to CSKA - wheeling away in delight with his finger raised after pouncing from close range.
With just minutes remaining, however, midfielder Bernardo Silva darted in to score the equalizer.
Riyad Mahrez struck the close-range winner in a 1-0 victory against FC Copenhagen that kept Leicester well on track for the next round after three straight wins.
Leicester coach Claudio Ranieri's tactic to keep Mahrez fresh just before Champions League games is proving decisive.
Mahrez was restored to the starting lineup after being rested on Saturday at Chelsea, only coming off the bench in the second half.
Prior to the previous Champions League game - a home win against Porto - he was substituted at halftime against Manchester United.
Five minutes before halftime, he acrobatically flicked in a header from fellow Algeria international Islam Slimani, after good work by striker Jamie Vardy.
Ranieri's team, shock winners of the Premier League last season, needs one win from its final three games to make the knockout phase.
Leicester is five points clear of Copenhagen and FC Porto, which came from behind to beat Club Brugge 2-1 and condemn the Belgian side to a third successive loss.
Emerging striker Andre Silva, who has scored four times in the last two games for Portugal, settled the match with an injury-time penalty.
Forward Jelle Vossen put Brugge ahead, but Mexican defender Miguel Layun leveled with a long-range drive.
Ten-man Juventus won 1-0 away to Lyon thanks to some shot-stopping heroics from goalkeeper Gianluigi Buffon and a brilliant winner from Colombia midfielder Juan Cuadrado.
He scored in the 76th minute after cutting in down the right, beating full back Jeremy Morel and launching an unstoppable shot into the near top corner from the tightest of angles.
Prior to that, Lyon had threatened an upset.
But Buffon saved a 35th-minute penalty from Alexandre Lacazette and then denied Lyon twice in the second half with remarkable reflex saves, tipping over forward Nabil Fekir's deflected shot when off balance and kicking away Corentin Tolisso's point-blank header.
The win kept Juventus top of Group H with seven points and ahead of Europa League champion Sevilla on goal difference.
Sevilla won 1-0 at last-place Dinamo Zagreb, with French midfielder Samir Nasri scoring from close range during the first half.