Lee, a graduate transfer from Drexel, considered Arizona, Gonzaga, Maryland and Marquette, before choosing the Cardinals.
"Knowing that I was the hot hand, it was just one of those things," said Lee, who made 4 of 7 3-point attempts. "It was just one of those things where I was confident. It was kind of like throwing the rock into an ocean. When I see the basket, I feel like I can get going."
Onuaku had 12 points and 10 rebounds — his eighth double-double this season — and Donovan Mitchell added 10 points. Lewis had nine for the Cardinals, who shot 53 percent in the second half and 43 percent overall.
"I thought our guys defensively and rebounding-wise, got up in a big time way," Louisville coach Rick Pitino said. "I'm real proud of them."
Justin Jackson scored 16 points and Brice Johnson had 15 for North Carolina, which shot just 35 percent from the field and committed 16 turnovers.
Louisville controlled the paint 36-28 and edged the Tar Heels 41-39 on the boards, with Onuaku's late grab looming large in a game where every possession was critical.
"Their zone made it difficult for us to get the ball inside to our big guys," North Carolina coach Roy Williams said. "We didn't move nearly as well as we needed to move inside and I think that was something that's really important as well."
The Cardinals obviously made some changes after Saturday's 63-47 loss to Virginia, when they shot a season-low 33 percent and committed 18 turnovers. Having Onuaku back in the starting lineup after being slowed by a stomach virus helped Louisville, though two first-half fouls limited his effectiveness.
He came up big in the second half despite two more fouls to help Louisville, which certainly needed to rebound against a North Carolina squad coming off a 27-point rout of Boston College and leading the ACC in scoring. And as it turned out, every rebound was important in keeping the Cardinals ahead in a rough-and-tumble game where baskets were hard to come by.
For a while, it looked like much of the offense would come at the free throw line with the Tar Heels' 12-of-15 accuracy helping somewhat offset their 29 percent first-half shooting. Marcus Paige particularly struggled, missing all five attempts from the field in the half before finishing with nine points.
Louisville was slightly better at 32 percent and somehow emerged with a 28-27 lead at the break despite trailing for much of the half. The Cardinals never trailed again and drew a little bit closer to North Carolina in the standings as a result.