When it's 90-plus degrees out, and the humidity is so thick that you can scoop it with a soup spoon, who wants a heavy meal? Who wants, come to think of it, soup?

But…wait a minute. What about gazpacho?

The soup of Spanish summers is an Andalusian godsend when the heat is on, a veritable cornucopia that refreshes and nourishes. It's vitamin-rich, low fat, high in dietary fiber and, in its most famous form, cholesterol free.

And, you know, it's served chilled. When it's 90-plus out, that hits the spot.

Don't know gazpacho from green beans? Here are four quick facts about this indispensable soup that some call a "liquid salad."

It's been around for centuries

It's generally accepted that gazpacho originated in the southern part of Spain, in the Andalusia region. It began as a simple dish, with simple ingredients like bread and vinegar and garlic and olive oil and salt.

It's mentioned as a kind of working man's food in the seventh-century novel "Don Quixote" (or, more fully "The Ingenious Gentleman Don Quixote of La Mancha," or, in Spanish, "El Ingenioso Hidalgo Don Quijote de la Mancha"). In the novel, Sancho Panza says, "I'd rather get my fill of gazpacho then be subject to the misery of an impertinent doctor that kills me with hunger."

The dish evolved over centuries, most notably when the Spanish brought tomatoes back from the Andes in the 1500s (though Italian Christopher Columbus may have brought them back to Spain and thrown them in a soup a little earlier). Cucumbers (from India), peppers and other vegetables followed, and soon variations on it emerged all over Spain.

Green gazpacho made with fennel and cucumbersA green gazpacho made with fennel and cucumbers. (Photo: cyclonebill/flickr)

There's more than one kind of gazpacho

The tomato gazpacho is the one known most widely. It's also known as "red" gazpacho or gazpacho Andaluz. This, from andalucia.com, which bills itself as the "premier online guide for useful information about Andalucia and Southern Spain":

"The original mixture is supplemented here with large quantities of [tomato] and smaller proportions of cucumber and green pepper. It is served garnished with green pepper, hard boiled egg, fried bread, onion, tomato and cucumber, everything being finely chopped."

There's a white gazpacho, too, with white garlic and almonds, often with fruits like grape, melon or apple included. And then there's green gazpacho, with green vegetables, parsley and the like. Other variations include meat or fish.

In real gazpacho, stale bread is a key ingredient

The first mentions of the soup almost always noted the inclusion of days-old bread, probably from the times Roman soldiers carried bread on long treks. Like many cultures the world over, the Spanish find ways to incorporate ingredients in their cooking that otherwise may be considered past their use.

In one of the earliest preparations, and one that continues to this day in parts of Andalusia, the stale bread is soaked, in either vinegar or water, to make it more palatable. It’s then added to garlic, vinegar, olive oil and salt in a big mortar to make a paste.

Some accounts believe that Columbus took this paste on his long voyages to the new world. Traditionally, workers in the field would take a break from the summer heat to eat it. Again, from andalucia.com:

“Each of the [men] has his own spoon. Gathered around the large bowl, they follow an ancient ritual whereby they approach after each other and then 'step back" at the moment of eating.'"

That was the beginning of gazpacho. And it’s grown from there.

It's not hard to make

Befitting its humble roots, gazpacho can be made very simply. Some recipes call for green peppers and tomatoes to be cooked a little so they can be peeled, cored, and their seeds removed. Others just have you stick it all in a blender, maybe strain it to remove the seeds, season it and let 'er rip.

You have to let it chill for a while, maybe as long as overnight, although it shouldn't be served icy cold. Still, the actual preparation of the dish should come in at well under an hour. Under a half-hour in many recipes.

The most difficult part of making gazpacho (other than finding the freshest of ingredients) is the chopping, dicing and mincing of ingredients. And getting the ingredients in the right ratios.

Gazpacho should be coarse, but not thick. It should be liquid, but not runny. If it's not thick enough, many recipes suggest more bread (old bread, if you have it). If it's too thick, some tomato juice or chilled water should do the trick.

Gazpacho now is mostly served before a meal, though in Spain they sometimes eat it before dessert, too. Whatever the case, a big bowl of gazpacho, seasoned exactly right (another trick that takes time to learn), can be a meal unto itself. It can be an astonishingly healthy, deliciously cool way to end a sizzling summer day.

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An ode to gazpacho, the soup of summer
The soup of Spanish summers is an Andalusian godsend when the heat is on, a veritable cornucopia that refreshes and nourishes.