Garbrandt was coming off three consecutive losses in the Octagon, and had not recorded a UFC victory since December 2016. However, the American fighter's passion for the sport has been reignited after Sunday's win.
"It feels amazing, it's been a journey," Garbrandt said after the fight.
"I went from the top of the world 11-0 to a three fight skid. I just want to thank everyone for sticking with me.
"I give these fights away when I brawl. My passion is back. A lot of fighters lose that and it's hard to find."
Garbrandt's professional record improves to 12-3 after UFC 250, while Assuncao suffers his third consecutive UFC loss.
Earlier, Sean O'Malley showed once again he is the real deal in the UFC and his latest knockout left jaws on the floor.
As O'Malley and Eddie Wineland felt each other during the opening round of their bantamweight clash, the mercurial star landed the telling blow and didn't even bother following up.
A slight fake saw Wineland drop his hands before O'Malley unleashed a hellacious right hand that put his opponent to sleep in an instant.
"That might be the greatest walk away KO we've ever seen," Joe Rogan said after the fight.
O'Malley wasn't shy when talking about the punch post-fight:
"I think that punch is worth $100,000".
However, Garbrandt's buzzer-beater is arguably more deserving of the Knockout of the Night accolade.
UFC 250 Las Vegas:
• Cody Garbrandt defeated Rafael Assuncao via KO – R2, 4:59
• Aljamain Sterling defeated Cory Sandhagen via submission – R1, 1:28
• Neil Magny defeated Anthony Rocco Martin via unanimous decision (30-27 x2, 29-28)
Sean O'Malley defeated Eddie Wineland via KO – R1, 1:54
