The 2018 Cup Series champion led 20 of 242 over-scheduled laps and prevailed in a late crossover battle with Kyle Busch to capture the inaugural Cup event in Madison, Illinois.
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 2020 NASCAR Xfinity Series champion commenced his first full-time campaign in the Cup Series by becoming the 41st different winner of the Great American Race.