"I thought I had lost, to be honest. I had to work hard for it today," Natzke said.
"I crashed in the first corner in my first race and came back from last to finish third, so that was good.
"In the second race I got an easy win and in race three I won again after a battle with Josh Coppins."
The two men had ended the day level on points, but Natzke got the nod for the trophy because he'd recorded more race wins in the MX2 class during the weekend. Natzke produced two wins to Coppins' one in their four races.
Natzke has long battled some of the top GP stars of Europe, with mixed success, before returning to sign up with the green bike brand and then immediately tasting success against one of the sport's legends.
Finishing 3-1-1 in the three MX2 races early in the day, Natzke lined up for his final outing, the all-capacity-bikes Shootout feature.
He settled for eighth overall in that novelty feature of the afternoon, one place behind Motueka's Coppins, with 450cc bike riders not-surprisingly claiming the top six spots ahead of them.
"I learned a lot from racing with Josh today. Where I had to pass him in that third race...any other rider I could blow past them, but Josh is so experienced and has so much race craft, that I had to dig deep."
Natzke has spent more than five years of racing in the United Kingdom, Belgium and Germany.
"I am loving the new bike and the Kawasaki guys around me are great. The geometry of the KX250F really suits me and I feel comfortable on the bike."
The icing on the cake for Natzke was also finishing third in the Speedcross final on Saturday evening, a stadium motocross event styled on international supercross tracks.
Natzke finished the stand-alone spectacle behind two 450cc bike riders, Mount Maunganui's Cody Cooper and Taupo's Brad Groombridge.
Meanwhile, his fellow Eni Oil Kawasaki Racing Team rider Flynn Watts also celebrated his debut ride for the squad with an overall runner-up finish in the 12-16 years' 85cc class during Saturday's junior racing at Taupō.
Watts finished with a 1-2-2 score-card on Saturday, narrowly edged out for the top podium spot by Invercargill's Jack Symon, who went 2-1-1.