Arturo Vidal's header gave them an early advantage and, despite heavy pressure at times from the visitors, held on to put them on a solid footing ahead of their trip to Lisbon.
Vidal strikes early
Bayern were ahead inside 120 seconds, and there was very little Benfica could do about it. The ball was switched to Franck Ribéry on the left, who cut inside before finding Robert Lewandowski on the edge of the area. He drove wide before teeing up Juan Bernat, and the Spaniard picked out the late run of Arturo Vidal. A powerful header from Vidal left Ederson Moraes rooted to the spot, and the hosts had the start they wanted.
Benfica weren't learning their lesson from the opener, as Douglas Costa was next to try his luck; Ederson was on hand to save from close range, however. In what was a completely dominant 20 minutes, a clever chipped ball from Thiago provided another chance to grab an early goal. He found Thomas Müller at the back post, but Ederson repelled the danger once more.
The Portuguese outfit's ventures forward were few and far between, though Nicolas Gaitán felt hard done by when his hand-ball appeal was turned down on Philipp Lahm. It would have been extremely harsh, though, as the Bayern captain was in the process of sliding to the ground.
The remainder of the half passed without major incident, despite Vidal going close with yet another headed effort. There was some concern over Renato Sanches, when the youngster went down following a robust challenge. He did bounce back up soon after, and that was quickly followed by the half-time whistle.
Benfica battle back
The second half began in the same way the first ended, with Bayern in full control. The first quarter hour of the second period provided little in the way of chances for either team, with Costa's blocked effort the only real moment of danger Benfica faced.
Instead the visitors grew as an attacking force and could quite easily have been level. First, Jonas had a strong shot well saved by Manuel Neuer. The opportunity that followed was the better of the two, as André Almeida burst down the right before cutting the ball back into the box. Jonas' effort was blocked by Martinez and the follow up was dealt with again by the Spaniard, before the third effort was blasted over from just a few yards out.
With the game growing stale and the clock counting down, both sides brought players off the bench in a bid to change the game. Bayern managed to create two late chances, but took neither. Ribéry's run and shot forced a good save from Ederson's foot, before Lewandowski failed to picked out Costa following a Vidal through ball.
Those passed up opportunities could prove crucial in Lisbon, but the hosts held on to claim an important advantage and clean sheet heading into the second leg. Benfica will be disappointed they failed to make the most of their own massive moments, though they have a real chance in the second leg of overturning the deficit.