"The Tooth", a short story by G. Gordon Dewey; reprinted in Science Fantasy, Vol. 4 No. 11, 1954 which is available at the Internet Archive.
about a restaurant serving (magical) food
"I never thought I'd wait in line to eat at any restaurant," the woman complained. "Why, there must be 500 people still ahead of us!"
"Now, Martha," her husband said soothingly, "the line's moving right along. We'll be in before you know it."
"If it wasn't that everybody was talking about the O'Loys and their wonderful new restaurant, and all, I wouldn't be here, I'll tell you!"
The line moved smoothly on, and before long Martha and her patient husband stepped through the doors of the Magic Kitchen. Then Martha forgot her recent annoyance.
It was a huge place, seating at least 1200 people at a time, high-ceilinged, clean looking, well lighted. There was the smell of good food in the air, and there was a look of cozy satisfaction on the faces of those who were leaving, their meals eaten.
that evaporated when you traveled several hundred yards
They were outside now, on the sidewalk, strolling along, sluggish, feeling the heaviness of their dinners.
Then, suddenly, the sensation of being stuffed was gone. There was only the feeling of having had a delicious dinner, one that left them with a pleasant warming glow.
The restaurant served real bread, so patrons won't be hungry when the glorious dishes they'd ordered (from the "whatever you wish" menu) disappeared.
"May I have your orders, please?"
"We haven't seen a menu yet," Martha reminded her sharply.
The young woman continued to smile. "No menus, Madam. Just order whatever you desire."
"How do we know what they cost?"
"One dollar a person, Madam, regardless of what you have."
For once in her life Martha felt inadequate as she ordered, ransacking her memory for favorite dishes. Sea food cocktail. Tomato juice. Avocado and fruit salad. Pheasant and bacon. Mashed potatoes. Green peas. Cold lobster on the side. Baked Alaska. Coffee. Cordial.
The young woman added the husband's order for bear steak and French fries, collected their money, and gave them their table assignment. They were scarcely seated when a waiter appeared with silverware and water, platters heaped with butter, and a huge covered dish.
When he had gone Martha lifted the lid gingerly. "Biscuits!" she snorted. "Well, I don't intend to fill up on biscuits!"
Her husband was hungrier. He broke one open, filled it with butter, popped it absent-mindedly into his mouth. He bit down, looked puzzled, and then his tired face beamed in delight. He started buttering another while Martha watched him suspiciously.
"Try one, Martha. You've never tasted . . ." Whatever he had planned to say was cut off as he began the second biscuit.
"Better than mine?" Martha's tone and expression were challenging.
"Well, all right—but I'm not going to let them spoil my dinner."
A few minutes later the waiter returned with their dinners, removed the empty biscuit dish, and put their food before them.
Possibly from Fantasy and Science Fiction in the fifties.
First published in The Magazine of Fantasy and Science Fiction, August 1952.
There was a good comment on this question yesterday, pointing out that the food disappeared after a certain time, not after a certain distance,
That was my comment, and I was remembering it wrong; it's distance, not time:
At last Mike sighed. "It's a good trick, honey," he said. "While it lasts. But once I get about 300 feet or so away from the house--Foop! Everything your Tooth makes just turns into thin air. . . . Very thin air!"
and that the good bread was actually nutrient fortified (good) rolls.
"I got it!" Grasping his wife's shoulders, Mike shook her excitedly. "I got it! I got it!"
"Unhand me, gorilla. Got what?"
"Look, darling! You can make the best biscuits in the whole wide world. Can you make them even better? Lots of them? Thousands of them? Millions? Zillions?"
"Slow down, bub—you're racing your motor. Why?"
"If you can, we're in! Could you chonk them full of vitamins and iron and hormones and amino acids and all those things? So they'd be nutritious and still delicious?
"Yes . . . I suppose so. I guess I could."
"We'll open a restaurant. We'll start out with a small place, then grow."
"It's all right. We'll let the customers order anything they want. Give them biscuits while they're waiting. Biscuits they won't be able to resist eating. They'll be filling, and provide all the nourishment a person needs. The biscuits alone will be worth what we charge for the rest of the meal."
"I don't know. It doesn't seem—I hope you're right. . . ."