Real, 3-0 up from the first leg in Turin, found themselves down to two Mario Mandzukic headers in the first-half and conceded a third when Blaise Matuidi netted after the break following a fumble by keeper Keylor Navas.
"In football nothing is given away, we have to fight until the end, today Madrid could have scored more goals, but Juventus and Buffon were good".
But Ronaldo, in his 150th Champions League appearance, then netted his 120th goal in the competition by converting the penalty with a firm shot into the top corner.
With the game in the 97th minute, Ronaldo made no mistake from 12 yards, ensuring a 3-1 defeat on the night but a 4-3 win on aggregate.
Zinedine Zidane gave a brief interview in the flash zone to BeIn Sports to give his thoughts on tonight's return leg against Juventus.
Buffon rushed toward Oliver immediately after the call and quickly got into his face to complain, prompting the red card.
The referee had wasted no time to point to the spot, the ensuing argument over the propriety or otherwise of the decision had threatened to snowball into a chaotic exchange emotions reached boiling point.
"The most important thing is we have the technology, it exists and is in use, so we have to bring it into the Champions League".
"I do not understand why they protest against the penalty", Ronaldo told beIN Sports after the Real Madrid vs Juventus match.
Juventus still won the match, 3-1, but Real Madrid will advance to the semifinal draw on Friday. "That allowed their team to grow, and it made things hard for us".
Sami Khedira hung a deep cross to the back post where Mandzukic powered a header past Navas.
"The first leg had given me confidence we could do this and the side deserved at least extra time", Allegri said.
Ronaldo failed to keep his header down four minutes from time when he escaped the attentions of Lichtsteiner to get on the end of Dani Carvajal's cross, but the Portuguese forward would have the final say.