With new interim manager Ralf Rangnick watching from the stands, the German was given a glimpse of both the talent he will have to work with and problems he has to solve at Old Trafford.
Arsenal went ahead in bizarre circumstances as Emile Smith Rowe’s shot trickled in with United goalkeeper David De Gea down injured before Bruno Fernandes levelled.
Ronaldo’s 800th career goal was quickly cancelled out by Martin Odegaard.
💯💯💯💯💯💯💯💯@Cristiano is out of this world 🌍#MUFC https://t.co/UaQjnCUNH0
— Manchester United (@ManUtd) 1638483246000
But the five-time Ballon d’Or winner had the final say when he crashed home a penalty 20 minutes from time.
A vital victory for United cuts the gap between the sides to two points in the battle for a place in next season’s Champions League.
Three points also rounds off a fine stint for Michael Carrick in caretaker charge since Ole Gunnar Solskjaer was sacked after progress to the Champions League last 16 and a creditable 1-1 draw at Premier League leaders Chelsea.
The United fans paid homage to Solskjaer with a banner in the first match at Old Trafford since he was dismissed.
Our minds are already set on the next game, there’s no time to celebrate! Today’s win was very important to get bac… https://t.co/nRNasyM0O1
— Cristiano Ronaldo (@Cristiano) 1638487513000
However, once the action got underway, nothing seemed to have changed from the final days of the Norwegian’s reign as United started in a similar fashion to humiliating home defeats to Liverpool and Manchester City.
Pierre-Emerick Aubameyang and Ben White had chances for the visitors inside the first two minutes.
When Arsenal did go in front on 13 minutes it was in strange fashion.
Smith Rowe’s shot bounced into an unguarded net with De Gea down injured having been stood on by his own player Fred.
Referee Martin Atkinson blew the whistle to stop play, but only after the ball had crossed the line and therefore the goal had to stand.
Arsenal players rebuffed United’s request to stand aside and allow them to equalise in a gesture of fair play.
But they did so of their own accord a minute before half-time when Jadon Sancho and Fred combined to tee up Fernandes to slot home his first goal since September.
In stark contrast to a cagey first 45 minutes, the second period raged from end to end.
De Gea made amends for his part in the opening goal with a flying save to deny Gabriel before Aaron Ramsdale produced an even better stop at the other end to divert Ronaldo’s drive to safety.
Ronaldo was dropped to the bench by Carrick at Stamford Bridge on Sunday amid suggestions that may become a more common occurrence under Rangnick’s high-energy style.
Accommodating the 36-year-old has been one of the causes of United’s decline defensively this season.
But Ronaldo has kept his end of the bargain with 12 goals in 17 games since returning for a second spell with the Red Devils.
He coolly slotted home Marcus Rashford’s cross, but United’s lead lasted just two minutes as Arsenal responded with almost a carbon copy equaliser.
This time Gabriel Martinelli was the provider for Odegaard to steer into the far corner.
However, on the night he reached another remarkable personal milestone, the stage was set for Ronaldo to breathe new life into United’s season when Fred was chopped down inside the box by Odegaard.
Fernandes blasted over when he retained penalty duties against Aston Villa earlier in the season.
This time he stood aside for his international teammate, who smashed the ball high past Ramsdale for his 130th United goal across two spells.
Ronaldo also scored 450 goals for Real Madrid, 101 at Juventus, five for Sporting Lisbon and is the record goalscorer in international football with 115 for Portugal.