Ewan’s top speed in the finale reached 68.8km/h.
Bennett crossed second and Nizzolo came third — both with the same time as Ewan.
Ewan, who rides for the Lotto-Soudal team, won three stages last year, including the coveted final leg on the Champs-Élysées in Paris.
Alaphilippe crossed with the main pack and retained a four-second lead over Adam Yates, with Marc Hirschi still third overall, seven seconds behind.
After the opening two stages in the Mediterranean city of Nice, the race veered inland over a 198-kilometre route to Sisteron, which is labelled the “Gateway to Provence”.
The route featured four minor climbs before a flat finish suited to sprinters.
Three French riders — Anthony Perez, Jérôme Cousin and Benoît Cosnefroy — broke away at the start and established an advantage of nearly three minutes.
Cousin was left to push on midway through the stage, and created a solo lead of just over four minutes after Perez and Cosnefroy settled back into the peloton.
Cousin was finally caught by the main pack with 16 kilometres remaining.
Perez, meanwhile, crashed into his team car on a high-speed descent after puncturing a tyre and broke his left collarbone — forcing him to abandon the race.
It was an especially unfortunate accident for Perez, since he had already gained enough points to don the polka-dot mountains classification jersey after the stage.
Stage 4 on Tuesday features the race’s first summit finish with a climb to Orcières-Merlette that should force the overall favourites — such as defending champion Egan Bernal — into action.
The three-week Tour, which was postponed from its usual July slot due to the coronavirus, ends in Paris on September 20.