She lost her father, Joseph Migliucci, 81, the longtime face of the Bronx restaurant, to COVID-19 in April.

The night before the elder Migliucci died, he asked his daughter to promise that she would do everything she could to make sure that Mario’s would reopen.

“He said, ‘Now you’re the boss, and you need to run the show,’ ” Migliucci-Delfino, 58, told The Post.

That’s meant adjusting the classic menu to changing times.

The restaurant’s neighborhood, Belmont, has launched “Piazza di Belmont,” an al-fresco dining plan that closes Arthur Avenue (between East 188th Street and Crescent Avenue) to cars from Thursday to Saturday evenings.

And while outdoor dining has been a saving grace for New York restaurants, the summer heat has posed a challenge to red-sauce establishments like Mario’s.

“They’re not eating like they’re sitting in air conditioning,” Migliucci-Delfino said. “If you’re sitting outside and it’s 90 degrees and the humidity is 100 percent, how much heavy food can you eat?”

Owner Regina Migliucci-Delfino at Mario’s Restaurant on the Bronx’s famed Arthur Avenue.

Annie Wermiel/NY Post

Joe Migliucci outside of Mario’s.

Annie Wermiel/NY Post

Also complicating matters: Spatial constraints and social-distancing rules have eliminated the large groups who would previously make the pilgrimage to Mario’s for massive family-style dinners.

“You’re not getting that party of 10 or 12 people on Saturday night that wants to sit together, eat together, drink together,” she said. “You’re just not getting that.”

The circumstances have forced the Mario’s team to get devise a menu that won’t result in as much waste if an item doesn’t sell on a particular day.

Pizza, which Migliucci-Delfino described as the restaurant’s “best-kept secret” over the past century, is being listed on the menu for the first time. Paninis have also become a lunchtime special for diners looking for something lighter than spaghetti and meatballs.

It’s not the first time during the pandemic that Migliucci-Delfino has had to figure out how to adapt.

After the restaurant closed in March, she was faced with thousands of dollars of meat and produce about to go to waste — so she gave it away.

“I was making care packages for the help, for my friends, to take home for myself,” she said.

“I’ve been working here 30 years. I’ve been coming in with my father since I was a child — I’ve never in my life experienced anything like this. He said before he died that he had never seen anything like this, and he was 81 years old. It was catastrophic.”

A family eating a meal at Mario’s Restauant.

Annie Wermiel/NY Post

Diners eating outside at Mario’s.

Annie Wermiel/NY Post

Some of the dishes on the menu at Mario’s.

Annie Wermiel/NY Post

Migliucci-Delfino admitted she is behind on payments to suppliers, and still waiting on more than $150,000 from the federal Paycheck Protection Program.

But signs are pointing toward a slight recovery, with crowds getting bigger every week since reopening.

The second Sunday in July saw the restaurant’s small staff serve 140 customers — a figure less than half of what it would be on a normal Sunday in July, but nonetheless impressive given the 11-table setup.

“I went home, I was hurting,” Migliucci-Delfino said. “But it was a good feeling to be tired. I went home happy.”