The Penguins built a 3-0 lead less than two minutes deep into the second period -- all of the goals coming on the power play.
Gordon's goal came on an individual effort in which he carried the puck into the offensive zone along the right boards, took it to the net and lifted the puck over Marc-Andre Fleury's glove.
The puck bounced off the back support bar of the net and play continued until the next break, when a video review determined Gordon's shot was a goal.
The Capitals won their third straight. The victory went to Jose Theodore, who made 23 saves.