It was the third goal in two post-season games for Bruin.
The Dynamo remained undefeated against the Eastern Conference regular-season champions in four meetings this year.
The second leg will be in Kansas City to determine a berth in the Eastern Conference championship series against either D.C. United or Red Bull New York.
Yosemite climber falls 30 feet, suffers major injuries
'How to Train Your Dragon 2' releases 5-minute clip