Bundesliga leaders Union Berlin again proved their season start is no fluke as they easily beat supposed title challengers Borussia Dortmund 2-0 at home on Sunday. Union took an early lead after Dortmund keeper Gregor Kobel slipped when trying to clear and presented Janik Haberer with the easiest goal he will ever score. More poor play from Dortmund’s backline allowed Union to engineer their second, with midfielder Haberer on hand to sweep in his second from the edge of the area on 21 minutes. The east Berliners, who only entered the Bundesliga for the first time in 2019 and still have a mostl…