ALLISON and Kevin Melanson's world revolves around one perfectly scrumptious, rapturously gorgeous tomato. Just which tomato might fit that description remains a mystery, a riddle they seek to solve in their own characteristically practical way.

 How to find the best one? Easy. They grow just about every type.

 In a typical year, the Melansons will grow at least 70 kinds in their Westchester backyard. And that's just varieties. Their total number of plants reaches into the hundreds.

 Get the Melansons talking about growing and eating tomatoes, and Kevin will fall into the rapid-fire Boston accent of his youth, so excited he sounds like Matt Damon on a Red Sox jag. Allison's eyes will often pop wide open like some character in a "Speed Racer" cartoon. Mention one of her all-time favorites, 'Cherokee Purple,' and she gasps.

 All of which makes the humble start of their tomato tale so surprising. Eight years ago, Kevin, a finish carpenter, and Allison, associate director of festivals at the USC School of Cinematic Arts, wanted to grow tomatoes in a whiskey half-barrel, so they bought six seedlings at Target.

 "I think the tag said the variety was 'Red.' Red tomatoes," Kevin says with a laugh.

 "No, no, they were Romas," Allison says. "They were adorable. But six to a barrel? We had no idea what we were doing."

 They failed miserably with that first crop -- a difficult trick, some might say. But a passion was born.

 In their second year as tomato gardeners, Kevin built raised beds with 2-by-10-inch pine boards. Just a few, he and Allison agreed.

 They imported soil from myriad sources, including dirt excavated from a neighbor's hillside, some fairly expensive mushroom compost recommended by a friend and a 30-cubic-foot bag from Home Depot. These amendments awakened the heavy clay soil that originally plagued the site. The tomato seedlings grew spectacularly. Other life that had been dormant arose from hibernation in biblical quantities.

 "Years two and three, I started calling myself the Grub Man," says Kevin, who adopted the strategy of sieving the soil to make it looser. "I'd get up to 150 big, disgusting grubs every time I'd sieve."

 At first he and Allison threw the grubs away.

 "But then we got the idea to put them out in trash can lids and feed the birds," Allison says, grinning.

 The garden took off. The number of raised beds grew to 17, and today the no-nonsense constructions are spilling over with tomato plants.

 Everywhere in the garden, the distinctive, spicy scent of tomato leaf loiters in the air. The plants are supported by handmade cages, crafted from heavy-gauge mesh fencing material that rises as high as 8 feet.

 "Some of these tomatoes want to grow that high. Last year we had a 'Carmello' get to 27 feet," Allison says, referring to a terrific heirloom. "Up and down the cage it went. And it was some of the best fruit we had."

 Push aside the bougainvillea cuttings sewn into the beds to keep pesky cats away, and you can feel just how dry the soil feels. The Melansons water deeply just once per week, and the plants seem just fine.

 Their fertilizer of choice: John & Bob's Soil Optimizer.

 "There's other really good fertilizer out there, and we've tried a ton of them, but they require mixing and multiple applications," Kevin says. "We're lazy."

  FOR help with their harvest, the couple has brought a veritable advisory board of tomato aficionados into their lives. Steve Goto, one of the Southland's primary growers of heirloom and hybrid tomatoes, is on their speed dial.

 Allison, now certified through the University of California's master gardener program, spends January through March starting seedlings for Jimmy Williams, known citywide for the eclectic vegetable transplants that he sells at the Hollywood Farmers Market.

 Kevin spends his spare time hunting for seeds that neither Goto nor Williams has heard of. Last year he found one called 'Krasnodar Titans,' an heirloom with large red fruit.

 But professional growers aren't the only ones filling their pots. At an anniversary dinner at Napa Rose in Anaheim, a waiter told them the restaurant's general manager had grown dozens of different types of fruit for the heirloom tomato salad. The couple countered, saying they were growing 80 varieties.

 Soon, Michael Jordan ("the one who can't jump," Kevin says) appeared at their table, and the trio fell into tales of tomato madness. Had they tried 'Lucky Cross'? How'd they like 'Noire Charbonneuse'? What's the story with 'Kilimanjaro'?

 On subsequent visits, the three talked about tomatoes until the restaurant closed while the staff waited patiently by the door.

 LAST fall Jordan gave the Melansons a 'Copia,' a yellow tomato speckled with red throughout. It's an enormous 2 1/2 -pound fruit that satisfies many of the Melansons' requirements for what constitutes a perfect tomato: big, beautiful and delicious.

 On their annual Thanksgiving drive to Yosemite, Kevin brought the 'Copia' with him into an In-N-Out. People stared. One woman asked, "Is that a pumpkin?"

 Kevin took out his tomato knife and began cutting quarter-inch slices for people to try.

 "Everybody had these huge grins on," he says. "It was so fun to see people trying and loving something they'd never had before."

 Of course, while they were eating, Allison says, she was busy saving the seeds in a napkin -- "so I could start them in January."

 -- Tony Kienitz