While retailers have done a great job promoting sweet onions, the flat yellow onions don’t get a lot of love in restaurants, said Dave Munson, corporate chef for Keystone Fruit Marketing, Greencastle, Pa.

“There’s so much interest from consumers and it’s such a wonderful onion — first cousin to the Vidalia with similar looks and flavor — we can’t figure out why that doesn’t blow over into foodservice,” Munson said.

Mayan Sweets out of Peru are Keystone’s longest-running sweet onion crop, he said, after Georgia’s Vidalias and Walla Walla sweets out of Washington.

Price could be one barrier to sales, he said. Especially today, as the soft economy forces chefs to squeeze every penny to keep their doors open.

One bright spot is the Vancouver, Wash.-based Burgerville chain, which reported a 15% to 25% bump in sales during its annual summer promotion of fresh Walla Walla onion rings.

“They’ve marketed them to the nth degree,” Munson  said, “and consumers look forward to them.”

Chefs in small restaurants will often pick up a few Peruvians from the supermarket for a daily menu feature, said Munson, who dices them into cheese omelets for breakfast and loves their sweet flavor in salads.

“Eating a Mayan Sweet raw is one of the best things you can do,” he said.

“Sweet onions shaved or cut in half moons pair beautifully with fruit — think peaches, raspberries and caramelized pecans. Or pick your favorite green, add sweet onion, tomatoes and artichokes and get the whole thing going with a bit of dressing.”

When it comes to chefs and sweet onions, “it’s a little slow out there,” said John Vlahandreas, national onion sales director for Wada Farms Marketing Group, based in Idaho Falls, Idaho.

“There are some great chefs who use only sweet onions,” he said. “They’re going to demand it because it’s a specialty they really want to play with.”

One big sweet onion fan is Rick Vargas, owner of Sonoma Wine Shop and La Bodega Kitchens in Sonoma and Sebastopol, Calif.

Vargas uses the onion’s sweetness to soften the acidity of tomato in a simple marinara sauce, and he is working on a new ravioli of slow-cooked onions with Port Reyes blue cheese in a port wine sauce.

“Higher prices on sweet onions for specialty uses don’t deter me,” said Vargas, whose parents are from Peru. “If you’re a quality place, then put your money where your mouth is. Any vegetable is only good if it’s fresh.”

Culinary Institute of America grad Josh Bonanno of Tampa, Fla., who works for a coffee roaster during the day, recently discovered certified sweet onions when the daughter of the president of National Onion Labs, a regular customer, gave him a 10-pound bag to try.

Bonanno served the onions sliced raw over steak and slipped them into a smoked fish dip at a bimonthly supper club he organizes with his brother.

After the five-course meal, he praised the onions in his blog and responded to guests who wanted to know where to buy them.

“I’ll never look at an onion the same way again,” said the 23-year-old cook, who munched on the sweets while preparing dinner and is sold on the idea of choosing only certified onions.

“If I’m making French onion soup, I won’t use a sweet onion because you want some of the bite to stand up to all that cooking,” he said.

“But if I’m making Vietnamese pho soup, which often has raw onions in it, I won’t use a regular spicy onion anymore. The sweet finish on the sweet onion doesn’t linger and ruin the rest of the dish.”