Dortmund celebrate one of the goals against Cologne (Photo: Reuters)
Poland international Lewandowski, who has seven goals in 10 games, scored either side of halftime after goals from Shinji Kagawa and Marcel Schmelzer had given the hosts an early cushion.
Borussia Moenchengladbach dropped to fifth on 17 points after Hoffenheim forward Vedad Ibisevic, starting for the first time after a months-long injury break, struck on 56 minutes to give the hosts a 1-0 win.
VfB Stuttgart’s Mexico international Maza rescued a 2-2 draw at Nuremberg with a header at the far post six minutes from time. The draw was enough to move them into third on 17.
Leaders Bayern Munich, on 22, travel to Hanover 96 on Sunday. Werder Bremen are fourth, five points behind, after drawing 1-1 at Augsburg on Friday.