NEW YORK — A day after a witness said R. Kelly kept a young lady under his garage’s boxing ring for sex, a former employee got on the stand and testified that the R&B superstar once had his girlfriends fight one another as punishment for misbehavior.

The supposed infraction came when numerous Kelly partners twerked at the singer’s January 2016 birthday party at his Chicago studio, the witness testified. The episode was not fully explained, but Suzette Mayweather, who worked for Kelly for years as an assistant, said on the stand that the women had “twerked for cake” in an apparent effort to get a slice of the dessert.

“He had to have them get on each other. I think they were fighting,” said Mayweather.

While Mayweather did not see the fight, she heard laughing, screaming and thumping coming from upstairs at the studio during the brouhaha, she testified.

“He didn’t like an incident where they were twerking for cake,” Mayweather said.

Mayweather was part of a team of employees for Kelly, who is accused of running an elaborate sex trafficking scheme targeting young women and girls at his concerts.

The “Sex Me” singer — who allegedly compared himself to Jerry Lee Lewis when explaining his attraction to underage girls — beat his accusers, spanked them as punishment for breaking his rules and locked them in rooms for days at a time, according to witnesses.

Mayweather said one of Kelly’s girlfriends once came to her in tears, showing her marks on her buttocks from where “Rob” spanked her.

She was also the victim of Kelly’s boss style, which included docking an employee’s pay with what he called a “fine.”

In one incident, Kelly called Mayweather about 1 or 2 a.m. demanding that she bring him sweet potato pie. Not wanting to disappoint, Mayweather took an Uber to Walmart.

“I purchased all of the Patti LaBelle’s Sweet Potato Pie,” she said.

“You thought I was going to fail your test,” she said to Kelly when she delivered the desserts to his studio.

“Well damn, Twin,” Kelly responded, using Mayweather’s nickname.

Mayweather also testified that Kelly sometimes forced his girls to remain in rooms for a long time, and that they needed his permission to use the bathroom, eat or get off the tour buses when they were on the road.