Marcus Rashford came off the bench to help Manchester United beat Omonia Nicosia.
The side from Cyprus took a lead in the first half.
After being introduced at the interval, Marcus Rashford scored eight minutes later and then set up Antony Martial to finish the job.
Late in the game, Rashford made it a three-point game, before the Greeks pulled one back for United.
Following United's chastening derby defeat at the weekend, Ten Hag made three changes with the headline being the return ofRonaldo.
The English forward saved his side from an embarrassing defeat, while the Portuguese forward missed several chances to score.
Neil Lennon, the former Celtic boss, managed the Omonia line-up which featured few star names and only one win in 26 European games.
The visitors made all the running in the first half an hour, but the Cypriots stood up and took their chance.
On 17 minutes, Antony was played through and tried to square the ball for Bruno to score, but the keeper committed a foul. The player played the ball too far behind his teammate.
Antony's 25-yard effort was brilliantly denied by Fabiano before the Iran forward struck.
Bruno carried the ball nearly 50 yards after a three-on-one Omonia break away. The formerNottingham Forest player superbly finished into the roof of the net after playing in the game.
The boisterous crowd in Cyprus celebrated wildly and United were rattled, so Ten Hag made a double half-time change with Marcus Rashford and Luke Shaw.
It paid off eight minutes after the restart, when Rashford was released by a raking ball down the left, and the England international had time and space to slam the ball into the net.
After the hour, Ten Hag introduced Martial and together they put their side in front.
Martial's second touch of the game began a one-two with Marcus and the third saw him finish with power a shot past Fabiano.
The clearest opening came when Diogo Dalot pulled the ball back to him eight yards out and he hit the post.
Instead,Ronaldo had to settle with an assist for United's third, firing a low cross into the six- yard area for a tap-in.
The spirited Omonia were not done yet though, and they were able to reduce the deficit almost immediately.
A play-off against a team dropping out of the Champions League to reach the knockout stages remains a possibility after United saw the game out.