The thumping victory left Bayern, who are chasing an eighth successive league title, top of the table on 67 points from 29 games, 10 ahead of second-placed Borussia Dortmund who visit bottom-of-the-table Paderborn on Sunday.
Lewandowski snapped his goal drought against Fortuna when he scored for the first time against them to give Bayern a 3-0 lead in the first half after a Mathias Jørgensen own goal and a Benjamin Pavard header opened the floodgates.
It also meant the Pole had netted against every current Bundesliga team, having failed to score in five league meetings against Fortuna either with Bayern or his previous club Dortmund. The striker’s brace took his season’s tally in all competitions to 43 goals and equalled his personal best, which was set in the 2016/17 campaign.
Bayern’s coach, Hansi Flick, who became the club’s first coach to win 22 of his opening 25 games in charge and surpassed Pep Guardiola’s record of 21, stressed he cared only about filling the trophy cabinet. “I am not interested in statistics, it’s about being successful and it was important for us after the Dortmund game not to let up,” he said, referring to Bayern’s 1-0 win at their closest rivals on Tuesday.
The left-back Alphonso Davies, who also got on the scoresheet with the fifth goal, added: “After our game with Dortmund we wanted to go out and show the same attitude.”
Werder Bremen boosted their chances of escaping relegation from the Bundesliga with a spectacular goal from Leonardo Bittencourt that gave them a lifeline 1-0 win at Schalke. The result left Bremen second from bottom but they moved to within two points of 16th-placed Düsseldorf.
A lacklustre first half failed to produce any fireworks but Bittencourt grabbed a potentially vital winner for Bremen in the 32nd minute when he unleashed a fine effort into the top corner from 25 yards.
The result left Schalke, who are coached by the former Huddersfield manager David Wagner, 10th and extended their winless league run to 11 games. It was also their fourth successive defeat since the Bundesliga resumed on 16 May.
The Hoffenheim substitute Ihlas Bebou scored with almost his first touch as they beat Mainz 1-0 away to boost their hopes of qualifying for European football next season. Bebou came on in the 38th minute for the injured Jacob Bruun Larsen and slotted home four minutes later against the run of play after collecting Diadie Samassékou’s ball over the top of the Mainz midfield.
Victory drew Hoffenheim level on points with Wolfsburg, but kept them seventh on goal difference, while Mainz stayed in 15th place, a point above the bottom three, after their fifth game in a row without victory.
The visitors also had a first-half penalty when Christoph Baumgartner was brought down in the Mainz box, but keeper Florian Müller got down well to deny Steven Zuber from the spot.
Javairô Dilrosun and Krzysztof Piatek each scored as Hertha Berlin continued their unbeaten run under their new coach, Bruno Labbadia, and climbed to ninth after beating Augsburg 2-0.
Dilrosun scored midway through the first half and Piatek added a second in stoppage time at the end of the game to see Hertha pick up a 10th point out of a possible 12 since the resumption.
Defeat left Augsburg precariously placed just four points above the relegation places. Hertha were in 13th place when the season resumed, but have hit a purple patch since the much-travelled Labbadia took over as their fourth coach of the season.
Eintracht Frankfurt’s Daichi Kamada scored with an 85th-minute winner to secure a 2-1 victory at Wolfsburg, lifting them five points away from the relegation zone. Frankfurt, without a win in their previous six games, struck against the run of play when André Silva was brought down in the box and scored the 27th-minute penalty himself.
Wolfsburg twice went close to an equaliser before the break but got their deserved goal in the 58th through Kevin Mbabu’s glancing header from Maxi Arnold’s eighth assist of the season. Kamada then scored the winner from a Bas Dost layoff for his second goal in two games. The Frankfurt substitute Lucas Torró was sent off for two yellow cards within three minutes in stoppage time.
Frankfurt moved up to 12th place, five points above the relegation play-off spot, while Wolfsburg stayed sixth.