The 19-year-old Argentina international opened the scoring in sensational fashion after less than three minutes when he sent a gravity-defying bicycle kick into the top corner - a goal which drew immediate comparisons to Wayne Rooney's famous strike in the Manchester derby 12 years ago.
However, not for the first time this season, the final scoreline did not tell the full story, with Everton squandering a string of presentable chances which could - and perhaps should - have seen them come away from the game with something.
The Toffees had almost three times as many shots as their visitors, but Man United scored with all three of their efforts on target to climb back up to sixth place with a fifth win from their last six league games.
As expected, Everton's first outing since the controversial 10-point deduction which sent them into the relegation zone began amid a cacophony of noise and boos as the home fans made their anger at the punishment known both before and after kickoff.
The anger temporarily turned into begrudging admiration courtesy of Garnacho's moment of magic in the third minute, with the youngster potentially ending the Premier League goal of the season contest with six months of the campaign remaining.
WHAT A GOAL ALEJANDRO GARNACHO!!!! 🤯🤯🔥🔥 pic.twitter.com/L9h1inY5rT— Sky Sports Premier League (@SkySportsPL) November 26, 2023
Rooney's similar strike was voted the Premier League's greatest ever goal, but Garnacho's was arguably even better and will immediately be catapulted into the discussion of the best the competition has ever seen.
It was a role reversal for Everton, who themselves had started quickly a number of times in recent matches, but Sean Dyche's side responded well and went on to dominate much of the rest of the first half as they looked to harness the red-hot atmosphere inside Goodison.
Dominic Calvert-Lewin saw one tame effort saved by Andre Onana shortly before another fan protest against the Premier League in the 10th minute, and it was the Everton striker who was mostly to blame for the wastefulness which ultimately cost his side.
Calvert-Lewin sent a free header straight at Onana from a corner shortly after the half-hour mark, before again being denied by the Man United keeper with a toe-poke moments later.
Abdoulaye Doucoure then skewed another glorious chance wide as Everton failed to take advantage of three clear openings within the space of two minutes, and it was a similar story shortly before half time when Calvert-Lewin nodded over and Idrissa Gueye sliced wide in quick succession.
Man United weathered the storm with manager Erik ten Hag watching from the stands as he served a one-game touchline ban, and Everton were made to pay for their profligacy 10 minutes into the second half.
Martial was initially shown a yellow card for going down under the challenge of Ashley Young inside the box, but VAR intervened and referee John Brooks subsequently overturned his decision and awarded a penalty, which Rashford fired past his England teammate Jordan Pickford into the top corner.
It was the first time all season that Man United had gone into a 2-0 lead, but even that did not feel safe and Onana needed to pull off an acrobatic save to deny Gueye's long-range strike just one minute after Rashford's penalty.
The points were finally secure for the visitors when they added a third 15 minutes from time though, as Bruno Fernandes threaded the ball through for Martial, who coolly dinked it past Pickford for his ninth goal from 17 career meetings with Everton.
There were still chances for Everton to register, with Vitalii Mykolenko hitting the bar and Jack Harrison unable to bundle the ball over the line from close range, but they failed to breach the Man United defence as the Red Devils became the first team to keep 500 Premier League clean sheets.
In addition to the win, clean sheet and much-needed goals for Rashford and Martial, Man United also welcomed Luke Shaw back from injury on a successful afternoon on Merseyside which leaves them sixth in the table.
Everton, meanwhile, remain joint-bottom following their points deduction, five points from safety following Luton Town's victory on Saturday.No Data Analysis info