World number 34 Bublik won on grass at Halle last month and scooped his second title of the season in Switzerland after bouncing back from a first-round loss at Wimbledon.
"This is my sixth title and I have played the greats of the game, but this final I will remember as one of the toughest I ever played," said Bublik. "It was complete torture."
Cerundolo was playing in his first tour-level final since 2021 having dumped out top seed Casper Ruud in the last eight on Friday.
Bublik will climb back into the top 30 on Monday after a resurgence which has seen him win 17 of 22 matches since the start of the Madrid Open in mid-April. He also reached the quarter-finals at Roland Garros.