The WBC title eliminator lived up to the hype as Ruiz Jr dropped his Cuban opponent three times en route to a 114-111, 114-111 and 113-112 victory.
The 32-year-old was fighting for the first time since his win over Chris Arreola in May 2021.
Ruiz Jr got off to a quick start and displayed his power after dropping Ortiz twice in the second round.
The Cuban challenger went down to the canvas for a third time in the seventh round, with the knockdowns earning Ruiz victory in Los Angeles.
"I'm ready, man. I'm hungry," Ruiz told Fox Sports afterwards. "I want to be champion again and bring that belt back to Mexico!"
Former WBC heavyweight champion Deontay Wilder, who is set to fight Robert Helenius in October, was in attendance and appeared open to Ruiz's challenge of an all-American heavyweight clash in the not-so-distant future.
"If Deontay wins in October, me and him are with the same management and we can make this fight happen," said Ruiz. "Let's get it on. I'm hungry and I want to be champion again and bring that belt back to Mexico."
Wilder, who has been out of action since his defeat to Tyson Fury in the tird fight of their trilogy, added: "Deontay Wilder is back and looking for great, exciting fights to give the fans.
"If that's what the fans want, let's do it."