‘WHAT is this?” asks Luciano Pavarotti, opening the box of Krispy Kremes I’ve brought him. He looks inside, then pushes it away.

“No,” says the tenor. “That I can live without. For me, it’s pasta – that’s my sin. And very, very simple sauces, like tomato, butter, oil. A little butter, more oil.”

We’re talking about food – the great Italian passion, second only to opera – in the apartment overlooking Central Park that Pavarotti has kept for the last 18 years.

Hanging in the foyer are life-size portraits of him and his secretary-turned-fiancée, Nicoletta Mantovani (looking studious in wire-rimmed glasses); elsewhere, pictures of Puccini and Verdi vie for wall space. There’s a white couch in the living room, as well as a computer and a gleaming black piano.

Pavarotti, however, looks pale and tired. He’d just flown in from Italy the day before for his performance at Madison Square Garden tonight. Now he sits behind his desk, mopping his brow.

He turned off the air conditioner, he explains, not because it would affect his voice, but because “I was talking with Nicoletta and she has a voice so little, so soft, I was not able to hear her.”

Now she is in the kitchen, Pavarotti says, mischievously, “cooking for me.”

“It smells like risotto,” he says, closing his eyes and inhaling. “Something with pumpkin.”

Then he laughs. “You believe that she’s my cook? No, not at all. She’s a producer … She brought ‘Rent’ to Italy and it was a triumph, absolutely.”

The one who cooks, it seems, is Nicoletta’s mother – and, occasionally, Pavarotti himself.

“I cook generally everything,” he concedes. “I’m not a great cook, but my pasta is not bad.”

And he is as passionate about pasta preparation as he is about hitting high Cs.

“Food is an art,” he says. “I think many people think it’s a superficial, stupid thing. They don’t respect the art of the cuisine. We should talk in detail of one

dish …”

In this case, pasta.

“The important thing is to buy a good pasta and really watch [it],” the maestro says. “If it says [cook] 11 minutes, give a look at 10.”

And choose the right canned tomatoes, he says. One time when Pavarotti was in Barbados, he couldn’t find his favorite kind. Luckily, his New York publicist was on the way over.

“I told him, ‘While you are coming, take some tomatoes.’ I won’t tell you the brand,” he tells me sternly, anticipating the question, “but they are beautiful, absolutely gorgeous. You have great tomatoes in America, you know.”

Great tomatoes or not, Pavarotti doesn’t believe in carbo-loading before a performance.

“I try not to eat much, to keep athletic,” says the singer, who turns 65 next month and doesn’t seem to have jogged for years. “I just lost 10 kilos” – 22 pounds – “in eight or nine days.”

His secret?

“Don’t eat!”

He’s not joking. He has just returned from a spa in Italy where his calorie count was pared from his usual hearty 3,000 a day to a skimpy 600.

“They prepare everything for you,” he says. “If you want, you can stay in bed, or if you like, walk or swim.”

But no matter how much weight he’s lost or gained, his voice is beautiful. I tell him that when my mother heard him sing “Nessun Dorma,” she felt she could leave her husband for him.

Pavarotti smiles, a weary grin.

“They say that,” he says softly, “but it’s never true.”

Luciano Pavarotti performs tonight with the young Roman soprano Anna Lisa Raspagliosi at Madison Square Garden; for tickets, $23 to $303, call Ticketmaster, (212) 307-7171.