The 22-year-old winger only joined the Terrors from Rangers last Friday and marked his home debut by giving Jack Ross’s side a priceless lead to defend when they head to the Netherlands next Thursday for the second leg of this Europa Conference League third qualifying round tie.
United, playing their first European match since being thrashed 7-2 on aggregate by Dinamo Moscow in a Europa League qualifier 10 years ago, were backed by a pumped-up home support inside a near-full-house Tannadice crowd of 10,181.
United boss Ross introduced Jamie McGrath – who signed on the eve of the match on loan from Wigan – for his debut in the 59th minute.
It proved an inspired move as the substitute was involved in the hosts taking the lead within two minutes.
Middleton received a pass from Dylan Levitt wide on the right and skipped superbly away from two Alkmaar players before playing a one-two with McGrath and curling home a lovely finish from the edge of the box, sparking delirious scenes inside Tannadice.
Mark Atkinson was at Tannadice and rates the players out of ten ...
9. Glenn Middleton
Scored a glorious goal after a quiet first half. Really grew into the match and his confidence will be sky-high after his strike. 8 Photo: Rob Casey - SNS Group
10. Steven Fletcher
The sort of performance United signed the Scotland forward for. Was a totemic figure in attack, winning flick-ons and linking play. Led the line with aplomb. Photo: Rob Casey - SNS Group
11. Tony Watt
Really tricky and creative in the opening period, always willing to drive with the ball. Faded a little but a fine night's work. 7 Photo: Paul Devlin - SNS Group
12. Substitutes
Jamie McGrath (7, above) marked his debut with an instant assist for Middleton. Ilmari Niskanen (5) came on to add legs and Nicky Clark (n/a) made a late cameo. Photo: Mark Scates - SNS Group