Despite that, it is Juventus -- for whom substitute Douglas Costa struck a post late on -- who hold the upper hand heading into next Tuesday's return in Turin, with the winners of this tie facing Manchester City or Tottenham Hotspur in the last four.
"Ajax have great quality. We suffered after their goal but we defended well and finished the game better." Ronaldo was making his first appearance since suffering a thigh injury playing for Portugal last month -- it was his first game for Juventus since netting the hat-trick that dumped out Atletico Madrid in the last 16.
The 34-year-old is aiming to win the trophy for the fourth year running, and his goal here came from the visitors' only attempt on target.
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.
- De Jong runs the show -
Frenkie de Jong is leaving for Barcelona, and the 21-year-old's eagerness to get on the ball and start moves here underlined why the Catalans were prepared to pay an initial 75 million euros ($84.5 million) in January to secure his signature.
However, it was the Moroccan international, Hakim Ziyech, who was the most prominent going forward in the first half -- one curling effort in the 18th minute was heading for the top corner before being tipped over by Wojciech Szczesny.
Ajax certainly should have scored in the 25th minute when Dusan Tadic set up Donny van de Beek, but his shot went agonisingly wide.
Juventus only displayed their attacking threat in patches, with Federico Bernardeschi lively and Ronaldo hooking one chance wide.
The latter was kept largely quiet, but he was afforded too much time and space by the Ajax defence as he opened the scoring with the last act of the first half.
Ronaldo collected a pass from the elegant Rodrigo Bentancur, spread the play to Joao Cancelo and then ran unhindered in a straight line into the box to head home his compatriot's perfectly flighted cross.
The Ajax fans greeted their team's return for the second half with a rendition of Bob Marley's Three Little Birds, and they were still belting out the words to their adopted hymn when they equalised within a minute of the restart.
Neres robbed Cancelo by the left touchline just inside the Juventus half and advanced before curling a shot beyond Szczesny and into the far corner.
However, despite exerted pressure after that, Ajax could not get a winner, and Costa nearly delivered a late sucker punch when he struck the woodwork.
Ajax are still very much in the tie, although left-back Nicolas Tagliafico will be suspended for the return after being booked here.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)