From the kick-off, Dax McCarty played a long ball to Cahill who won his aerial contest on the right flank before following up with a well-struck half-volley from the edge of the area which gave Dynamo keeper Tally Hall no chance.
Cahill, whose goal beat the old record of 11 seconds, was thrilled to have entered his name into the MLS records.
"It was a big game for us and the ball got played into me from the middle of the park, I took it on my chest, took a bounce and it ended up in the top corner," he said.
"That was a massive win for us and it's a proud achievement for myself and obviously the MLS."
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