Luke Shaw's 12th-minute own goal means United have another Champions League mountain to climb on the road, after overturning a 2-0 first-leg deficit to eliminate Paris Saint-Germain on away goals in the last 16.
For Ronaldo, it was a 125th goal in the competition, and 24th in quarter-finals.
"It was a hard game and complicated at times, but we had the clearest chances".
"Ronaldo showed that he is on a different level".
Disney+ to debut November 12, will cost $6.99 a month
Disney will also contend with a new streaming service from Apple, which is expected to be released in the fall. Disney Plus will focus on family-friendly content, including a live action Star Wars series.
"Happy to come back and score another goal in this unbelievable competition".
Portugal right-back João Cancelo clipped a superb ball into the box to meet the run of Ronaldo, who powered his header past Ajax goalkeeper Andre Onana.
Ajax had set up this tie by ending Real Madrid's European hegemony in the previous round after a thrilling 4-1 victory in Spain, and maintain hope going into the return.
He said: "One-one is not the result you hope for, but it is a result".
The club were anxious to have the issue settled by the end of the month, with his existing contract due to expire in June 2020, but there have been no further public developments since that time.
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Following his death, political and community leaders were as quick and effusive in their praise as his fellow hip-hop artists. The man suspected of killing him, Eric Holder, has been charged with murder and two counts of attempted murder.
Elsewhere, an intriguing contest in London between Tottenham Hotspur and Manchester City ended with the home side securing a 1-0 win thanks to a late goal from Son Heung-Min.
Year after year the 34-year-old has produced when his team need him most.
Hakim Ziyech was a thorn in Juventus' side and he produced two good shots from range before forcing Wojciech Szczesny into a fine save when he finished off a spell of pressure by curling a 20-yard effort towards the top corner.
It was his 25th goal of the season - he has now scored six Champions League goals at the Johan Cruyff Arena, as many as ex-Ajax star Zlatan Ibrahimovic.
Ajax, however, wasted little time to find a way back into the game, as David Neres equalised for the hosts inside the opening minute of the second period.
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The 2.49% additional fee is the "crypto liquidation fee", which is apparently incurred every time you make a transaction. This is the first debit card to link directly with a major cryptocurrency exchange in the United Kingdom and EU.