Johnny Russell scored twice before being sent off as Dundee United eased to a 3-0 victory in the first competitive Dundee derby in seven years at a packed Tannadice.
A Gavin Gunning header after 14 minutes put Peter Houston's men ahead before Russell netted twice in three minutes just before the break to give the Terrors an unassailable lead.
Both sides had to play the final 20 minutes with 10 players after Russell and Dundee captain Stephen O'Donnell saw red for violent conduct.
The win moved United to the top of the Scottish Premier League as it maintained its 100 per cent record, while Dundee was left still looking for its first victory and goal of the new campaign.
Scottish Premier League
Ross County manager Derek Adams has extended his contract until the northern summer of 2016.