For the 2019 season, he drove for Deldiche Racing in the Belcar championship. He escaped major injuries during a crash at Assen that year after he collided with Kenneth Heyer at high speed. Heyer's car was launched into the air and landed on top of Boonen's Norma M20FC, narrowly missing Boonen's head by centimeters. In addition to his Belcar campaign, he also initially signed a deal to compete part-time in the NASCAR Whelen Euro Series with PK Carsport but the deal never materialized.