The hosts marked Mirko Slomka's first game at the helm in style and Calhanoglu put the icing on the cake when he lined up a free-kick 50 yards from goal as the game entered stoppage time.
With the Dortmund players seemingly expecting the Turk to play a simple short pass, they decided against forming a wall and Calhanoglu duly sent a swerving, dipping effort beyond Roman Weidenfeller and into the top left-hand corner of the goal.
But Calhanoglu insisted that it was the sort of finish that he tries all the time on the training pitch.
"I hit the free-kick the same way I do in training all the time," he told Bundesliga Live.
"I'm delighted that I pulled it off!
"It's an absolute dream to be able to beat Dortmund. We're in a much better place now."
"I've seen him do this before in training," he said.
