By that stage it was already 1-1 as Antony cancelled out Alex Iwobi’s opener for Everton.
Ronaldo took his chance just before half-time to give United a deserved three points from an error-strewn game by both sides.
Victory takes Ten Hag’s men up to fifth and within nine points of leaders Arsenal with a game in hand.
The Red Devils were seeking a response to being thrashed 6-3 by Manchester City last weekend but got off to the worst possible start.
On his first Premier League start since arriving for £60 million ($67 million) from Real Madrid, Casemiro was culpable for the opening goal as he was robbed in possession by Amadou Onana and the ball eventually broke for Iwobi to curl into the top corner from outside the box.
Everton came into the game with the best defensive record in the league, but were quickly undone as United levelled within 10 minutes.
Antony became the first United player to score in his first three Premier League games with a cool finish from Martial’s pass.
Martial only lasted 30 minutes after pulling up with a hip injury in the warm-up and his departure paved the way for Ronaldo to make his entrance.
The 37-year-old has had to get used to life on the sidelines under Ten Hag.
However, Ronaldo gave his Dutch coach a reminder of the predatory instincts he retains.
Casemiro made amends for his earlier error by winning possession in midfield and playing in his former Real Madrid teammate to fire low under Jordan Pickford.
That strike took Ronaldo’s tally in two spells with United to 144.
Madrid’s record goalscorer hit 450 for the Spanish giants, while he scored 101 times for Juventus and five for Sporting Lisbon.
Ronaldo should have had a second just before the hour mark as he nodded wide from another teasing delivery from Casemiro.
Everton had been on a seven-game unbeaten run, but offered little in the search of an equaliser until a late aerial assault and were lucky to avoid conceding a third goal 10 minutes from time.
Marcus Rashford pounced on a mistake by Iwobi to round Pickford and slot into an empty net, but the United forward was penalised for handball by a VAR review.
