Adam Rooney’s 18th and 19th goals of the season (36 & 89) were enough to extend the leaders’ advantage over Celtic and their run of league wins, all of which have been secured without conceding.
And the scoreline flattered third-bottom Motherwell, who survived several near misses and lost Stephen McManus to a harsh red card in the incident that led to Rooney scoring his second from the penalty spot.
Aberdeen dominated from the start and it was a busy afternoon for home goalkeeper Dan Twardzik, who got in the way of David Goodwillie’s early shot and then adjusted his feet to palm away an overhit Jonny Hayes cross.
In-between those two scares Rooney let Motherwell off the hook with a wayward header, but Aberdeen’s top scorer then timed his movement well to run on to Goodwillie’s chipped pass and slide a left-footed finish between Twardzik’s legs.
The keeper got a fingertip on Niall McGinn’s curler, helping it against the bar to keep the half-time score at 1-0, and when he was beaten after the break Andrew Considine’s header came back off the far post.
The introduction of teenager Dom Thomas did spark Motherwell into life in the closing stages, but Aberdeen keeper Scott Brown’s duties remained routine, and Goodwillie twice missed chances to put the game to bed on the break.
Rooney was not so profligate and sent Twardzik the wrong way from the spot after McManus, who could do little to get out of the way, was sent off for handling Hayes’ shot on his own goal-line.