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 ...
5. Kieran Freeman
Stationed in an unnatural left-back position, AZ targeted the young full-back. While he had some uncomfortable early moments, he grew into the game. 6 Photo: Ross MacDonald - SNS Group
6. Dylan Levitt
Another classy and cultured display from the midfielder, who looked right at home on this stage. Pinpoint long-range pass started the goal. 9 Photo: Mark Scates - SNS Group
7. Craig Sibbald
Diligent with the ball and tenacious without it. A fine midfield display, only tarnished by a yellow card that resulted in his earlier-than-anticipated withdrawal. 8 Photo: Ross MacDonald - SNS Group
8. Ian Harkes
Part of a midfield that looked the match of their opponents. Some of his passes didn't come off but was always willing on the ball. 7 Photo: Paul Devlin - SNS Group