The Netherlands international scored with a curling effort in the first half as the Bavarian giants registered a 1-0 win at the Allianz Arena.
"It was all about the joy and happiness of having won the game," he told Bayern's official website. "When I'm on the pitch, it's simply about winning.
"A match like that against Dortmund is always special. When you settle a match like that, with a goal like that, you've got to be a bit chuffed."
Bayern are currently 17 points clear of Dortmund at the top of the Bundesliga table.