Bayern routed Fortuna Dusseldorf 4-0 away, while Gladbach lost at promoted Union Berlin 2-0.
Lewandowski had scored in every Bundesliga game so far, but the Polish forward couldn't stretch his league record to 12 games against Fortuna - still the only side remaining in the 18-team division against which he hasn't scored.
It wasn't for lack of trying. Lewandowski sent one shot narrowly wide of the post and his powerful header was saved well by goalkeeper Zack Steffen. He even tried a scissor kick, without success.
Goals from Benjamin Pavard, Corentin Tolisso, Serge Gnabry, and Philippe Coutinho gave Bayern its second straight 4-0 win in the Bundesliga after routing Borussia Dortmund before the international break.
It stretched Bayern's winning run to three games under Flick, Germany coach Joachim Low's former assistant. Flick is filling in for the fired Niko Kovac and has yet to see his side concede.
Bayern became the first visiting team since April to leave Düsseldorf with a clean sheet.