UFC featherweight champion Amanda Nunes dominated Felicia Spencer and scored a comprehensive decision victory on Saturday in retaining her crown, becoming the first two-weight UFC champ to successfully defend both belts.

The Canadian challenger went the distance at the UFC 250 event at the UFC Apex in Las Vegas on Saturday, but she was completely outclassed, as Nunes won every one of the five rounds on the judges' scorecards.

Amanda Nunes of Brazil punches Felicia Spencer of Canada in their UFC featherweight championship bout during UFC 250 at the UFC APEX, in Las Vegas, NV, USA, on June 6, 2020; Photo: Jeff Bottari/Zuffa LLC via USA TODAY Sports

"I studied her very well, I know she's tough and I have to be sharp if I have to go five rounds, I have to be dominating," a beaming Nunes told commentator Joe Rogan after the fight.

"That was my goal, defending my two belts at the same time. I defended both belts, you know, I'm the greatest! I'm so happy right now!" she added.

Spencer fought bravely but her limitations were exposed early on as Nunes caught her with a stiff jab and then took her to the mat, where she controlled her with ease.

Amanda Nunes of Brazil punches Felicia Spencer of Canada in their UFC featherweight championship bout during UFC 250 at the UFC APEX, in Las Vegas, NV, USA, on June 6, 2020; Photo: Jeff Bottari/Zuffa LLC via USA TODAY Sports

A flurry of punches by Nunes the end of the second round almost put a stop to the contest, and Spencer somehow survived a late choke attempt at the end of the fourth, although her forehead to swelled up heading into the final round.

With Nunes barely breaking a sweat, the doctor was called into the octagon late in the fifth to examine a cut on Spencer, but the 29-year-old was able to battle on to the end of a one-sided contest that cemented Nunes' status as one of the sport's most dominant champions.

After beating Miesha Tate to win the bantamweight belt in July 2016, the 32-year-old Brazilian has been on a tear for almost four years, defending that title with violent knockouts of former champions Ronda Rousey and Holly Holm.

She then stepped up to featherweight and added that title by demolishing the much-feared Cris Cyborg in just 51 seconds, knocking her unconscious with a superb display of boxing in December 2018.

The problem for Nunes and the UFC now is that there is no challenger on the horizon that looks capable of threatening Nunes, who hasn't lost since she was knocked out by Cat Zingano in September 2014.

"I don't know what is next, but I've proved (myself) already. Tonight I closed a cycle, and I'm proud of myself and my team," Nunes said.