Williams came out of the blocks with three straight games for 3-0, and, after Cirstea got on the board with a pair of games herself to close to 3-2, the No.1-seeded American shifted back into cruise control, reeling off the next nine games in a row to complete a 62 60 championship win in 65 minutes.
"I knew she had had a lot of big wins and a lot of momentum going into this match," Williams said. "She also had nothing to lose out there, so I knew it wasn't going to be an easy match for me today.
"I knew I had to play better today than last night. With that in mind, I just tried to do that."
"I think the start wasn't as bad as the score showed - I actually had really good chances in all of the first three games," Cirstea said. "Sadly I found myself down 3-0 a little bit too quick. I managed to get back to 3-2, but 4-2 was an important game, and I had kind of an easy ball to get to 4-3 but missed it.
"She got better as the match went along. And I wasn't able to pick up my game as I was in the past few matches. But all credit to her - there's a reason we have the rankings and why she's on top of those rankings. She's the No.1 player, and she's proving that every single time she steps on court."
Williams took home her third Rogers Cup, also winning the Premier-level event in 2001 and 2011. And she now has 54 WTA titles to her name, breaking a tie with Monica Seles for standalone ninth place on the all-time list for WTA titles. The only eight players who have more career WTA titles than Williams are Martina Navratilova (167), Chris Evert (154), Steffi Graf (107), Margaret Court (92), Evonne Goolagong-Cawley (68), Billie Jean King (67), Lindsay Davenport (55) and Virginia Wade (55).
The American also had some star support in the crowd as she went for that 54th WTA title. "Drake came out today," she said. "We are really good friends. We have always been good friends. It was good to see him come out and good to see him in Toronto. So I was excited that he made it today."
She also had kind words for Cirstea in her trophy speech, after the Romanian was visibly emotional.
"You're so young, I wish I was 23, don't be sad!" Williams said to Cirstea after giving the Romanian a big hug. "You've beaten so many top players this week and you're really such a good player."
She then turned to the crowd: "Sorana's one of the nicest girls on tour and has such a bright future."
Cirstea has a lot of positives to take away. Firstly, she recorded her 10th, 11th and 12th Top 10 wins along the way over Caroline Wozniacki, Petra Kvitova and Li Na, her win over the No.5-ranked Li matching her previous-best wins over No.5s Jelena Jankovic and Sam Stosur. Secondly, she reached her first Premier-level final - her other two finals both came at International-level events. And finally, she is projected to reach a new career-high No.21 on Monday, just inches from her Top 20 debut.
"It's been a really positive week, and I'm going to take everything that's been going well with me to the next tournament," Cirstea said. "I think I've made great steps in the past weeks - I've played semis, quarters, finals here - so I'm looking forward to everything coming up and also the US Open."