Wayne Simmonds also scored for Toronto, and Jack Campbell made 20 saves. The Maple Leafs rebounded from a 3-2 loss at Ottawa on Thursday night, to improve to 2-10.
''It's extremely important,'' Simmonds said about getting production up and down the lineup. ''That's gonna pay dividends going down the rest of the year.
''We've got a lot of high-octane offensive guys, but on a nightly basis sometimes guys aren't clicking and it's up to everyone else.''
Josh Norris scored Ottawa. Anton Forsberg made 26 saves after stopping 46 shots Thursday in the season opener.
''Second and third period, we played as hard as you have to play to win a game in the National Hockey League,'' Senators coach D.J. Smith said. ''But you can't feel your way into a game on the road.''
The attendance at Scotiabank Arena was announced at 18,211, the second straight home date short of a sellout.
Toronto was forced into an uncomfortable situation behind Campbell with fellow netminder Petr Mrazek (groin) and defenseman Justin Holl (illness) sidelined Saturday.
Pressed tight to the NHL's salary cap - which remains stagnant at $81.5-million because of the COVID-19 pandemic's economic fallout - the Maple Leafs didn't have enough room on their books to recall No. 3 option Michael Hutchinson from the minors without sending someone down and playing with 17 skaters.
Faced with that option, the club instead signed University of Toronto goalie Alex Bishop, who played three seasons in the Quebec Major Junior Hockey League, to a one-day amateur tryout to serve as Campbell's backup.
''Jack got through the game and was good, comfortable,'' Maple Leafs coach Sheldon Keefe said. ''It's an unfortunate situation that's a reality of the flat cap system, and the fact that for the first time in the flat cap, you don't have the exemptions and things that were in place for COVID last year. You're going to see a lot of this throughout the league.''
Simmonds opened the scoring just 2:12 into the first period after Toronto won an offensive-zone faceoff. Rasmus Sandin took a pass from defense partner Travis Dermott and rotated down low before feeding the bruising winger at the top of the crease.
''To be able to play in my hometown and have my wife and daughter at the game ... it's been really nice,'' said Simmonds, who waited nine games last season for his first goal as a Leaf with the team playing in empty buildings. ''All the fans in general, it's been unbelievable.''
Toronto doubled its lead at 8:06 when William Nylander, who has points in all three of the Leafs' games, stole the puck from Ottawa rookie Shane Pinto down low. Nylander fed it in front to Kerfoot, who made no mistake on Forsberg.
Toronto defenseman Morgan Rielly hit the post early in the second before Forsberg robbed John Tavares with a terrific glove save later in the period.
The Maple Leafs then got a 5-on-3 power play for 1:06, but Forsberg denied Tavares on a one-time effort.
The Senators finally broke through on a late power play when Tyler Ennis won a battle and Drake Batherson found Norris in front.
Batherson appeared to even things up with five seconds left in period on a breakaway that saw his initial shot rebound off Campbell, off the Ottawa forward's leg and in. But Toronto correctly challenged for offside.
Bunting finally gave the Leafs some breathing room at 7:57 after taking a pass from Kerfoot on a 2-on-1.
''A moment I'll remember for the rest of my life,'' Bunting said. ''It was a cool experience to be able to get one at home for my first time and celebrate in front of that crowd.''
Senators: Host Dallas on Sunday.
Maple Leafs: Host New York Rangers on Monday night.
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