Manchester United celebrate during their win at Everton
Garnacho's incredible third-minute effort silenced the fiery home faithful at Goodison Park, as fans vented their fury with anti-Premier League protests following their unprecedented sanction.
There looked to be no danger when Diogo Dalot dinked a cross into the box, but Garnacho had other ideas, taking a couple of steps back before leaping into the Merseyside sky and unleashing an unstoppable bicycle kick that sailed over Jordan Pickford and into the net.
The goal was the only chance United created in the first half and Everton will be left wondering how they did not go in at least level at the break.
Dominic Calvert-Lewin was the home side's main culprit in their flurry of chances, drawing decent saves from Andre Onana and sending a gilt-edged headed opportunity over the bar.
United, without suspended manager Erik ten Hag on the touchline, gave a debut to impressive 18-year-old Kobbie Mainoo and the midfielder made a superb clearance off the line to deny Dwight McNeil.
Everton were made to rue their numerous misses as Ashley Young was adjudged to have tripped Anthony Martial in the box and Marcus Rashford stepped up to confidently score the penalty.
United captain Bruno Fernandes, who usually takes the spot-kicks, handed the ball to Rashford to give him a chance to score only his second Premier League goal of the season.
"I think he needed a goal," said Fernandes. "I am really happy he scored - a boost of confidence for him."
Ten Hag added: "You see how great a captain Bruno is. He assessed that his team-mate needed that goal. As a team you need that leadership that you back each other."
Martial finished off a slick team move for United's third as they moved up to sixth in the Premier League, while Everton are in significant trouble at the bottom end - in 19th position and five points from fourth-bottom Luton Town.
-- Courtesy of BBC Sport