Just a week after Xabi Alonso's Bayer Leverkusen broke Bayern's 11-year title run, the visitors were dominant and clinical in the German capital.

Kane curled in an excellent free-kick and laid on a second-half goal for Mathys Tel. The England captain is eight shy of Robert Lewandowski's single-season Bundesliga goals record with four games remaining.

Bayern rested Jamal Musiala after Wednesday's 1-0 win over Arsenal sent them through to the Champions League semi-finals but they had no difficulty creating chances against Union.

"We're happy -- it was a perfect week. It was by no means guaranteed that we'd win like that," said Bayern coach Thomas Tuchel.

Handed a rare start, French teenager Tel set up Leon Goretzka's 29th-minute opener, with Kane doubling the lead in first-half stoppage time.

Mueller, playing his 470th Bundesliga game for Bayern, scored both of his goals in the second half, either side of a strike from Tel.

"We fought hard from the get go and played well right up until the end," said Goretzka.

"We've still got a huge target in the Champions League and we want to keep the season alive."

Union, who faced Real Madrid and Napoli in the Champions League this season, pulled one back late through Yorbe Vertessen, have now won just one of their past eight and sit three points clear of the relegation places.