The 20-year-old Australian finished ahead of Avanti's Patrick Bevin and Drapac's Bernard Sulzberger and now also holds the points and best young rider classifications jerseys.
The third stage was a 99km circuit (six 16.5km laps) which featured only one small climb per lap, but repeated attacks and a late split in the peloton kept the pace high.
"We knew (the Iranians) were always going to be really aggressive today" Ewan said. "It was obviously a pretty hard course and the team just rode so perfectly.
“We used Jens (Mouris) and Heppie (Michael Hepburn) to start with and they were just so strong and really neutralised all the attacks.
“I think it made those guys think twice about attacking so they (Ewan's teammates) could ride a little bit easier on the climb for me.
“Obviously we knew in the last two laps we probably wouldn’t be able to control it that much, because the guys that aren’t sprinters obviously had to go around them.
Five riders hatched an early escape but Drapac and ORICA-GreenEDGE combined at the head of the main field to block further breaks and kept the rest of the stage under control. The final five kilometres belonged to ORICA-GreenEDGE as it delivered Ewan to another sizeable victory.
"The last two laps were really hard. I thought there were only maybe Mitch (Docker) and I left on the last climb, but the whole team came back together,” Ewan said.
“I knew the main climb was going to be hard but I didn’t expect the two climbs beforehand to be as tough. It really takes it out of you and when they really go hard on the last climb it really, really, hurts.”