He never looked troubled, despite the numerous restarts and yellow flags.
"It's pretty unreal and I don't really know what to say," said an elated Cassidy. "The target for the race was to get out front and control the race. I didn't need to set the fastest lap all the time because there were always gong to be safety cars.
"All I needed to do was hold everyone at bay and I've had enough experience with this race to know you're not gong to win it by racing away.
"After every restart I put in a fast lap and then controlled the race pace.
"There was a little left at the end that was there if I needed to hold off the others."
Winning the internationally recognised NZGP sets a solid platform for Cassidy at the beginning of 2014 and sends out a good message for anyone domestically and internationally looking for a driver who can jump into a car and go fast straight away.
Cassidy raced under the banner of newcomers to the TRS championship, Neale Motorsport, who had another reason to celebrate the weekend. Team principal and owner Andrew Neale has a rich history in motorsport but never dreamed he'd be winning the NZGP, and his young charge Andrew Tang would clinch the overall championship in the last race of the series by finishing third.
The Singaporean driver has been Mr Consistency over the past nine races, never finishing off the podium and came to understand that points mean prizes.
"It's like a dream come true and I can't even put it into words," said Tang. "The race was a bit tricky but third was good enough to win the championship.
"After the first round in Invercargill it was like someone flicked a switch. The car has been awesome and I can't thank Andrew enough and also my mum and dad who have been so supportive of me going racing."