Leading 2-0 from the first leg at the Wanda Metropolitano, the Atletico coach Diego Simeone warned that Juventus were not just a matter of Ronaldo.
So wrong. The 34-year-old was their scourge. He halved the aggregate deficit after 27 minutes and brought the sides level just after half-time.
With the tie heading for extra-time, Angel Correa brought down Federico Bernardeschi in the penalty area. Referee Bjorn Kuipers pointed to spot.
Ronaldo, who moved to Turin at the start of the season for 100 million euros, thrashed home to complete the scintillating comeback.
"It was a magical night," said Ronaldo after the game. "I am very happy not only for my goals but for the whole side. We are a great team and we showed that anything can happen."
While Juventus left it late to win 3-0 and move into the quarter-final draw, Manchester City were in training ground mode during most of their second leg against Schalke.
Leading 3-2 after the first leg in Gelsenkirchen on 20 February, the tie was effectively over in eight first-half minutes at the Etihad Stadium.
Sergio Aguero scored City’s first from the penalty spot after Jeffrey Bruma’s clumsy challenge on Bernardo Silva.
Aguero stroked in the second following Raheem Sterling’s slick lay-off and Schalke old boy Leroy Sané got the third on the stroke of half-time.
Down 6-2 on aggregate, it was just a question of damage limitation for the Bundesliga strugglers against the English Premier League pacesetters.
Schalke failed to stem the tide against a merciless City who added further goals in the second half via Raheem Sterling, Bernardo Silva, Phil Foden and Gabriel Jesus.
"We are happy to get to the quarter-finals," Manchester City manager Pep Guardiola told BT Sport. "We didn't start that well, we were a bit scared to play. But after it went to 1-0, we relaxed and decided to play and be aggressive.
The 7-0 annihilation is unlikely to bolster the prospects of Schalke coach Domenico Tedesco. The 33-year-old's job has been under scrutiny after a slump which has taken Schalke towards the Bundesliga drop zone.