Guerin had two power-play goals to go with two assists while putting nine shots on goal and Kunitz had a score and three assists. Pittsburgh produced seven consecutive goals -- five of them coming in the second period.
The Penguins bounced back after being the victims of Martin Brodeur's NHL career record 104th shutout Monday. That loss to New Jersey snapped Pittsburgh's five-game winning streak.
Malkin scored in each period. His goal in the second came with 1:33 left and gave the Penguins a 6-1 lead.
Marc-Andre Fleury got the win with 45 saves. Pittsburgh moved into a tie with New Jersey atop the Atlantic Division with a league-high 53 points.
After being out of action since Nov. 23 with a fractured cheekbone, Ottawa goaltender Pascal Leclaire returned Wednesday and gave up six goals on 24 shots through two periods. Brian Elliott, who started 15 of the last 16 games, made 10 saves in the third.