Four of us were dining in a full house at Le Lion d'Or

on a Thursday night. We requested the Pritikin Diet

--no oil , no butter, no cream--and neither Paul

Haudy, the ma.itre d'h.otel, nor chef Jean-Pierre

Goyenvalle was about to leave this restaurant critic and Nathan Pritikin, the diet guru himself, in the lurch.

Appetizers were easy: three house salads of watercress, mushrooms, endive and the like, Pritikin's dry and the others' tossed with a vinegar and mustard concoction. The fourth appetizer was lobster salad, perfectly cooked cold lobster tail and claw surrounded by tiny bundles of slivered mushrooms, hair-thin green beans, shreds of carrot and celery on tiny red leaves, peeled and seasoned tomato wedges, all on pale leaves of oak-leaf lettuce, garnished with a few cooked rings of onion and an intriguing feathery and peppery cress.

French rolls were declared salty but eaten anyway; porcelain shells of butter were waved away. Then came the highlight, an enormous silver tray of vegetables, an array of brilliant colors and cunning shapes: broccoli florets and carved bites of zucchini, quartered artichoke bottoms, slender grean beans and halved tomatoes--ripe ones--baked with fresh basil, asparagus, fennel, turnips, spinach and carrots, all sprinkled with chives. It was a $26 vegetable platter, but what price art?

Main courses honored simplicity rather than invention. A thin, grilled, smoky-flavored paillard of veal; a grilled rockfish, crusty and peppery and cooked to a nice steamy juiciness; poached salmon topped with rings of onion and flowers of carrot, but poached a few moments too long. Dessert was strawberries and raspberries in stemmed glasses.

Dinner for four came to just under $150 before tip. Goyenvalle said that while the menu always has plenty for a dieter--fresh vegetables, fish to poach or grill, chicken or veal--with three days' notice he could provide dishes to order. Would he devise a very special diet meal?

"Any time," Goyenvalle promised.

But, Goyenvalle was asked, why not put a couple of such diet dishes on the menu?

Goyenvalle drew himself up a little and declared, "We are not a diet restaurant."