Real Madrid 1-3 Juventus – Juve seemed set to match the heroics of fellow Serie A side Roma against Barcelona at the Stadio Olimpico 24 hours earlier after surging into a 3-0 lead in the Spanish capital, only for Lucas Vazquez to draw a foul in the box and Ronaldo to settle the contest from the spot.
That came after lengthy delay in which Gianluigi Buffon saw red – the veteran goalkeeper’s first dismissal in his 117th, and final, outing in the competition.
Mario Mandzukic’s first-half brace, both headed efforts, sparked life into a contest that looked over after the first leg in Turin.
And when Keylor Navas – who seemed unsettled without suspended captain Sergio Ramos in front of him – fumbled a Douglas Costa cross at the feet of Blaise Matuidi, Massimiliano Allegri’s side drew level in the tie with half an hour of the 90 still to play.
Extra time beckoned but a clumsy challenge on Vazquez by Medhi Benatia saw referee Michael Oliver point to the spot, Buffon sent off for his vociferous protests, meaning Wojciech Szczesny came on to face the penalty.
Ronaldo – who hit a double including a stunning overhead kick in Madrid’s first-leg win – duly smashed home a nerveless spot-kick to maintain his sensational run of scoring in every game in this season’s Champions League, on what was his 150th appearance in the competition, to spare Madrid’s blushes.