Kas Beekmans powered to the win at Donington Park as he held off Harrison Dessoy for the full race.
The Dutchman took the lead from pole and never looked under too much pressure as he crossed the line 0.405secs clear of Dessoy.
Ash Barnes ran a steady race in third place to eventually take the final podium place with Ferre Fleerackers fourth and Rhys Stephenson fifth.
Pirelli National Sportbike Championship, Race One result.
1. Kas Beekmans (VLR/NIWA Racing)
2. Harrison Dessoy (PHR Performance Triumph) +0.409s
3. Ash Barnes (Raceways Yamaha) +4.070s
4. Ferre Fleerackers (B.art Racing Team) +6.396s
5. Rhys Stephenson (Rocket Racing) +7.030s