Grilled meat, slices of onion, a little tomato, maybe some peppers and a tortilla.

The ingredients can be summed up readily. These are clearly the makings of a taco -- unless, of course, they are served up on sizzling cast iron.

At restaurants around the world that presentation is known as a fajita. Diners follow its trail from kitchen to table, drawn by the cracking and popping and wisps of steam.

Dos Arcos in Mexico offers fajitas with beef, chicken, shrimp or all three. They even pare it down to a manageable lunch portion.

As with every favorite, there are several claims to the first fajita. The most notable are a Texas concessionaire dubbed "The Fajita King" and Ninfa's, a Houston restaurant that became an institution after putting fajitas on the menu.

Yet the origin of this wildly popular Tex-Mex platter can be traced to simple tacos prepared from an unwanted cut of beef. Even Ninfa's owner Ninfa Rodriguez Laurenzo first listed the dish as tacos al carbon.

So what happened? Well, almost every dish goes through an evolutionary process. And fajitas are something of a rags to riches tale.

Most food historians agree that what became fajitas began on the ranches of west Texas.

It was common during cattle roundups to slaughter an animal to feed ranch hands. Mexican cowboys were given less desirable cuts like the skirt steak to cover part of their wages. These were people adept at making tough pieces of meat edible. The result was a taco of thinly sliced and grilled skirt steak.

So far there is nothing remarkable. The practice of folding a tortilla over meat was centuries old.

A graduate student at Texas A&M named Homero Recio traced the nickname "fajita" to these ranch taco, with the earliest anecdotal mention from the 1930s. And an Austin Chronicle writer, Virginia B. Wood, speculated in a 2005 article that because the skirt steak is such a small portion of the meat taken from a carcass -- and because skirt steak was not marketable at the time -- familiarity with fajitas was contained to Texas ranch lands.

Vaqueros, their families, perhaps a few dusty village butchers knew the name. Restaurant owners and chefs, probably not.

Yes, it is likely people in other locales grilled up skirt steak for tacos or other dishes. Throughout history necessity has forced cultures to use all of an animal. But the name and presentation are more important aspects of the story. A grilled skirt steak dish known as arracheras had been a staple of Mexican families ranching along the borderland for some time.

Fajitas seemed destined for obscurity. But that changed suddenly.

In 1969 The Fajita King -- the title Sonny Falcon would later claim -- opened a fajita taco stand at a festival in Kyle, Texas. According to a 1993 article in the Texas Monthly, fajitas also appeared on the menu of Round-Up Restaurant in the ranch town of Pharr that same year.

Restaurant owner Otilia Garza reportedly was simply continuing a skirt steak tradition passed down from her grandmother, except that she added a notable twist: a sizzling hot platter and an array of toppings, a do it yourself taco.

Ninfa's introduced fajitas -- again, first as tacos al carbon -- to their menu four years later.

It took almost a decade for fajitas as we know them to explode on the national scene. In 1982 "sizzling fajitas" landed on the menu of the Hyatt Regency in Austin. As Woods reports, the dish quickly made the Austin Hyatt's restaurant the most profitable across the entire hotel empire.

By 1984 fajitas were in such demand that Recio, the Texas A& M student working on a graduate degree in animal science, noticed a sharp increase in the price of skirt steak and began following the trail.

But the lowly cut could no longer keep up.

And so at Dos Arcos, you can choose between beef, chicken, shrimp or go for a meatless version. But trying all at once works out nicely.