Nick Woltemade flicked in Sandro Tonali's shot to give Newcastle the lead in Brussels before Gordon converted twice from the spot on a comfortable night for Eddie Howe's men.

Harvey Barnes came off the bench to add a fourth as Newcastle responded well to a stinging Premier League defeat by Arsenal on Sunday and an opening loss in Europe to Barcelona two weeks ago.

Newcastle's two most expensive summer signings Woltemade and Anthony Elanga started alongside Gordon for the first time with the club looking to move on from the acrimonious departure of Alexander Isak to Liverpool.

Woltemade struck his third goal since arriving from Stuttgart for a club-record £69 million ($92 million) fee, getting a touch on Tonali's volley to wrong-foot home goalkeeper Kjell Scherpen and give Newcastle the lead on 17 minutes.

Elanga earned a penalty shortly before half-time after he was clattered by Fedde Leysen, with Gordon tucking it away to double Newcastle's advantage at Anderlecht's stadium, Union's temporary home as their own does not meet UEFA standards.

Sweden international Elanga tested Scherpen straight after the interval before Union enjoyed their best spell. Nick Pope saved well from Adem Zorgane and Ousseynou Niang moments after Anan Khalaili steered narrowly wide for the Belgian champions.

Newcastle were awarded a second penalty following a VAR review for a handball by Kamiel Van de Perre, and Gordon made no mistake with another clinical spot-kick just past the hour.

Union, who beat PSV Eindhoven 3-1 on their Champions League debut last month, saw their 10-match unbeaten run in all competitions come to a jarring end as Barnes wrapped up a convincing Newcastle victory by rounding off a breathless counter-attack 10 minutes from time.