In the co-main event, 27-year-old Paul stopped fellow American Mike Perry in the sixth round.
Perry, 32, left the UFC in 2021 and has become one of the most recognisable faces in the emerging bare-knuckle fighting scene in the US.
Paul floored Perry with an overhand right inside the first minute of the fight and again with a powerful right early in the second.
The bout was stopped midway through the sixth of the eight rounds as Perry – his face bloodied and swollen – stumbled after climbing off the canvas once more.
“He’s tough as nails but I just hit too hard and he took a lot of damage,” said Paul. “Mike Tyson, you’re next. It’s anyone, any time, any place.”
According to statistics from Compubox, Paul landed 96 punches to Perry’s 33 and had 52 of his 142 jabs connect, earning praise from the loser.
“You did a great job, you were way too fast for me and I couldn’t adjust,” admitted Perry.