GREAT GAZPACHO is impossible without great tomatoes. They are the main ingredient and should be scrutinized, held up to harsh light and inspected for flaws.

Unfortunately, when the Food section chose the best of 12 recipes, local tomatoes were not yet in season. Supermarket "vine-ripened" tomatoes which were little better than their hothouse clones, had to be substituted. But this cold Spanish soup/salad deserves dimpled, deep red beefsteak tomatoes worthly of a seed-catalogue cover. [Health-food shops, like the P Street Store, now have good ones at $1.89 a pound. You will have better and cheaper luck in supermarkets at the end of this month.]

However, despite vegetable inadequacies, a clear winner emerged -- one which was surprisingly different from the classical formulas.

According to Aldelina Calahan, co-owner with her husband of El Bodegon Spanish Restaurant, each region of Spain has its own version of gazpacho. One of Calahan's chefs, Pepe, is from Seville and makes it like this:

"You take white bread, not crust, and fry in olive oil until toasted, and in a mortar mash bread, garlic, green pepper, onion, cucumber and a little bit of tomatoes, whole black pepper and salt to taste. Mix in a little olive oil. Then add a touch of vinegar, some water and chill. Serve ice cold."

The bread is what keeps the Andalusians happy. Calahan says: "In some parts of Southern Spain, people won't eat gazpacho unless a spoon stands up in it." However, in northern Spain it is served without bread or croutons and thinned down with water.

The spanish Embassy recipe agrees with Pepe's

"pound 1 clove of garic and salt in a mortar and pestle. Add 4 ounces moistened bread crumbs with vinegar and work into a paste. And 2/3 pound of tomatoes, mash in with puree mixture. Add the heart of 1/2 pound cucumber and 2 or 3 pieces of the peel. Strain to puree texture. Place in a bowl and mix with diced tomates [1/3 pound], remaining cucumber pulp and 2 green peppers. Chill, and before serving add salt and vinegar to taste. Garnishes of chopped egg, cucumber, green pepper and garlic croutons can be added.

Other variations include gazpacho Colorado [red gazpacho served hot with crusty bread] and white gazpacho [hold the tomatoes].

But whenever the variations, purists agree on the following rules:

Chop, dice or mash the ingredients with a mortar and pestle if you like it smooth. A blender aerates the mixture, making it too fluffy and pablumy.

Use the best tomatoes avaiable. Tomatoes juice and canned tomatoes are cheating. [Even so, tomato juice was used in the tasters' choice.]

A light French or Spanish olive oil is preferable to vegetable oil, and red wine rather than cider vinegar.

Do not substitute garlic powder for fresh garlic. [As in any recipe, the powder doesn't have the right oomph].

Make the soup/salad a day before serving so that flavors get a chance to ripen.

In the dozen recipes tested, the main ingredients varied -- canned cream of tomato soup, beef bouillon, cumin, pimientos in place of tomatoes.

Each gazpacho was placed in glass jars, marked with letters, and given a rating from 1 to 5. The only authentic Andalusian recipe sent in [by Marilyn Price of Oxon Hill] was unappreciated by all but one taster who praised it highly. Most of the members wBEST, From M1> were not used to the texture of the bread. So much for authenticity.

The winning recipe is from Karen Eckhardt of Laurel, Md., who said, "I've been told by several airline stews that my gazpacho is better than what they serve in Spain."

ECKHARDT GAZPACHO [8 large servings] 1 can [46 ounces] tomato juice 5 beef bouillon cubes 3 medium tomatoes, chopped 1 cup chopped unpared cucumber 3/4 cup chopped green pepper 1/2 cup chopped scallions, with tops 8 tablespoons red wine vinegar 4 tablespoons vegetable oil 1 tablespoon Worcestershire sauce 1/2 teaspoon hot pepper sauce 1 large clove garlic, crushed

Heat tomato juice and bouillon cubes until dissolved. Stir in the remaining ingredients and chill for at least 12 hours. The soup is best if made a day in advance of serving.

Serve ice cold, over a bed of crushed ice, with seasoned croutons and a wedge of fresh lime. CAPTION: Illustration, no caption