The 24-year-old Byron from Charlotte, North Carolina, led a race-high 212 of 403 and fended off Joey Logano during an overtime shootout to repeat as a Cup winner at the Paperclip-shaped short track.
The 2018 NASCAR Cup Series champion will be making a one-race return to the Truck Series for David Gilliland Racing next weekend on Bristol's dirt layout.
The Alva, Florida, native bumped AJ Allmendinger and Alex Bowman out of the racing groove on the final lap to earn the first win in NASCAR's premier series for himself and Trackhouse Racing in Austin.
The Mitchell, Indiana, native became the 200th different competitor to achieve a win in NASCAR's premier series following his first career victory in the desert state.
The reigning NASCAR Cup Series champion led four times for 28 of 200 laps and fended off the field in a four-lap shootout to claim his second victory at Auto Club Speedway.
