Plant dominated the fight by outboxing Truax from a distance, while Truax tried unsuccessfully to get closer and force the action at close range.
Álvarez ended the fight in brutally conclusive fashion but he admitted that Plant had been a difficult opponent who had shown great skill and made the first half of the bout a highly competitive and absorbing contest.
Now the former two-time titleholder is back in business.
In March 2019, his mother, Beth Plant, was shot by police after pulling a knife on an officer.
Growing up in a two-bedroom trailer, Plant and his sister did not enjoy the riches of life.
He won the fight by a first-round knockout, ending the fight after just 47 seconds.