The visitors had high hopes of becoming the first Dundee side to win at Tannadice since 2004 but they were annihilated by Robbie Neilson’s men, who surged seven points clear of the Dees after just four games of the season.
There was little doubt United would maintain their perfect record so far in the league once they’d stormed into a 4-1 half-time lead courtesy of Calum Butcher’s brace, allied to further strikes from Louis Appere and Lawrence Shankland – from the penalty spot – with Kane Hemmings only briefly equalising in 21 minutes.
In the end history would repeat itself from New Year’s Day 2015, when United also chalked up a memorable 6-2 derby triumph at Tannadice.
Ironically, it was Dundee who thought they’d opened the scoring in eight minutes. Jamie Ness slipped in Danny Johnson and the striker steadied himself before despatching a finish into Benjamin Siegrist’s far corner, only for it to be disallowed for offside.
United, though, took the lead against the run of play. Peter Pawlett’s corner was headed back across goal by Mark Connolly and Butcher cleverly looped a header into the net despite the best efforts of visiting keeper Jack Hamilton.
Yet Dundee refused to buckle and dragged themselves back on level terms six minutes later. Ness’ free-kick was nodded down by central defender Jordon Forster to Hemmings, and the striker bundled the ball home at the second attempt.
Their joy at being back level was short-lived. Another Pawlett set-piece delivery wasn’t properly cleared, leaving Appere to smash home a shot via the underside of the bar. The contest was effectively over minutes later when Declan McDaid bundled into Paul McMullan in the area and Shankland smashed home the resultant spot-kick.
Butcher headed home another Pawlett corner just before the break, then substitute Ian Harkes wasted no time in getting No 5 just after the restart, his shot from 22 yards taking a deflection off Forster on its way into the net.
Dundee came to life when Andrew Nelson finished at the far post on 69 minutes but United weren’t finished and Cammy Smith, another substitute, cut in from the right and dragged a shot past Hamilton at his near post for No 6.