Alonso had to slam on his breaks, after Bortoleto strayed into the path of the Spaniard's Aston Martin when attempting to defend his position from Liam Lawson.
Quick reactions from Alonso prevented a huge smash, with rookie Bortoleto admitting after the race that he simply had not seen Alonso in his mirrors.
Part of that includes the pair sharing the same flights to race locations, and back, but Alonso joked after the incident that Bortoleto may have to go hungry on the way back from Saudi Arabia.
"Maybe no dinner for him," Alonso told media after the race.
Bortoleto and Alonso's dismal starts continue
Both Bortoleto and Alonso are two of four drivers who have not managed to score a single point in 2025 so far, with the former rooted to the bottom of the drivers' championship standings.
Bortoleto's much more experienced team-mate Nico Hulkenberg has scored all six of Sauber's points so far, as the team find themselves in an awkward transition period.
Sauber will become Audi in 2026, and new regulation changes sweeping into the sport for next season will potentially allow for a shake up of the competitive order, giving teams like Sauber/Audi more of a chance if they can master the new rules.
Meanwhile, the team are scratching around for the odd point here or there, although they have already beaten their points tally from a dismal 2024 season, just five races into the new season.