Stipe Miocic reclaimed the heavyweight title with a fourth-round knockout of Daniel Cormier at UFC 241, while Nate Diaz enjoyed a winning return.
Saturday's rematch went in favour of Miocic, who used a flurry of punches late in the bout to trouble Cormier before the referee stopped the fight at four minutes, nine seconds.
Miocic (19-3) was fighting for the first time since losing his title to Cormier (22-2) at UFC 226 in July 2018, ending the latter's nine-fight undefeated streak – dating back to January 2015.
Cormier got off to a fast start at Honda Center in Anaheim, where he landed several hard punches before slamming Miocic into the canvas during the opening round.
Miocic was more aggressive in the second round, though champion Cormier continued to cause problems inside the octagon.
The pair exchanged blows in round three, though neither took a back step, despite Cormier stunning Miocic with a right hand in the closing minute.
Miocic shocked Cormier in the fourth and he went on the attack, prompting the referee to halt proceedings as the former became the fourth UFC heavyweight champion to lose his belt and regain it.
Elsewhere, welterweight star Diaz (20-11) defeated Anthony Pettis (22-9) by unanimous decision in the co-main event on Saturday in his first appearance since losing his rematch against Conor McGregor in 2016.
Meanwhile, Paulo Costa edged Yoel Romero in an epic middleweight clash that was decided by unanimous decision.