The Australian won stage 11 for Lotto-Soudal in a drag race of a sprint in Novi Ligure, the hometown of Italian great Fausto Coppi.
Tuesday's winner Arnaud Demare of Groupama-FDJ came home second to take the lead in the points classification ahead of Bora-Hansgrohe's Pascal Ackermann, who had to settle for third on the day.
Ewan had jumped on to Ackermann's wheel on the final approach and bided his time before launching again.
"(Ackermann)'s one of the quickest here and he was the first sprinter that came past me," the Lotto-Soudal rider said. "My guys got me in a good position and it made my run a whole lot easier. I could just sit there and then time my sprint to perfection.
"My team have done a great job all week and I'm a little bit more relaxed going into the stage with one win already. When you're more relaxed you save more energy and everything seems to fall into place more easily."
But there was more frustration for Italian champion Elia Viviani, who could only manage fourth place as he was caught out of position.
The Deceunick-QuickStep rider now looks set to leave the race with three second-placed finishes to his name as he turns his attention to the Tour de France.
The sprint finish meant no change to the general classification, with UAE Team Emirates' Valerio Conti keeping the pink jersey with an advantage of one minute 50 seconds over race favourite Primoz Roglic of Team Jumbo-Visma.
Mitchelton-Scott's Simon Yates remains in 13th place, more than five-and-a-half minutes off Conti's time.
It was a sprint which almost appeared to play out in slow motion as they rode into a headwind down the long final straight at the end of a 221km stage from Carpi which had hardly been raced at a rapid rate.
Three riders, Marco Frapporti (Androni-Giocattoli-Sidermec), Mirco Maestri (Bardiana-CSF) and Damiano Cima (Nippo-Vini Fantini-Faizane), had been allowed to go clear, building a lead of around six minutes on the old Roman road of Via Aemilia.
But with the sprint teams massing on the front, aware this was their final chance, they were finally reeled in with 26km to go as a cagey battle for position began.
Ackermann had launched his sprint first but though he faded, he can be happy with third place given the injuries he sustained in a late crash on Tuesday.
All the same, he must now hand over the points leader's ciclamino jersey to Demare, with the Frenchman moving 11 ahead in the standings.
Yates and others with time to make up will now look to Thursday's stage as the more mountainous tests begin with a 158km stage from Cueno to Pinerolo, highlighted by the late ascent of Montoso, a category one test.
Those sprinters with an interest in the points classification may well be the only ones to take the start given the climbing to come as there are few other rewards open to them between here and Verona, and many of them have eyes on the Tour de France in July.
