Bayern, on track for a treble of titles after advancing to the Champions League quarter-finals with an extra-time victory over Juventus this week, are on 69 points, with second-placed Borussia Dortmund in action against Augsburg on Sunday.
The Bavarians are also chasing an unprecedented fourth straight Bundesliga title.
"I have to congratulate my players because it was very hard for them two-and-a-half days after playing 120 minutes in an emotional game against Juventus," said Bayern coach Pep Guardiola.
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"We controlled the game well but we felt how difficult it is to defend our titles this season."
Poland forward Lewandowski notched his 25th goal of the campaign with a well-placed shot in the 10th minute and Bayern were rarely threatened by the hosts in a one-sided game in which the visitors had more than 70 percent possession.
Hertha Berlin edged past Ingolstadt 2-1 to remain on course for a sensational third-place finish, opening up a four-point gap over Schalke, who are fourth.
Andre Schuerrle's last-gasp goal rescued a 1-1 draw for VfL Wolfsburg, who also reached the Champions League last eight, against Darmstadt 98 and they remained in eighth place.
Hoffenheim gave their hopes of remaining in the Bundesliga a major boost with a 3-1 victory at Hamburg, their third win in the last four matches.
After spending most of the season so far in the bottom two, Hoffenheim's victory lifted them into the relegation playoff spot.
(Reporting by Karolos Grohmann. editing by Ed Osmond and Ian Chadband)
