Spurs dominated the early stages, keeping the Arsenal defence busy as Arsene Wenger’s men struggled to keep possession.
There was then three yellow cards in as many minutes for Hector Bellerin, Erik Lamela and Francis Coquelin.
But the Gunners stunned the White Hart Lane crowd when Welbeck escaped down the left and rolled the ball across the penalty area for Bellerin, whose pass picked out Ramsey in the six-yard area and he back heeled the ball past Hugo Lloris.
They then had a couple moments to extend their lead before half time but were denied by errant passes.
After the break, the game changed when Coquelin was shown second yellow card for a stupid lunge on Harry Kane.