As I write, far from the tumble of orange lantana that bloomed on an adobe wall outside Nana's kitchen window in Mesa, a change comes upon the room. At times like this, portraits fall off the wall or knickknacks go flying—signs that my late grandfather is unhappy with my train of thought. He is right, for the creation of the Rosarita brand was his dream, not Nana's. My grandmother wanted other things; near the end of her long life, she told me that if she had it to do all over again, she would be a singer with a band.

To tell the story of Rosarita accurately, you must do so at lunch, the way Tata always did. Lunch was the big meal at my grandparents' house. Nana cooked without recipes, never sharpening her knives and rarely serving Rosarita products. She made turning out her flour tortillas look easy. First, she'd remove her rings, placing them in a teacup by the sink. Next, she'd roll a moist dough into small balls, then slap them into submission between her palms, tugging at their edges until they were as thin as handkerchiefs and as large as dinner plates. Though her formula was standard—flour, lard, water, a little salt—her technique was brilliant; they still talk of Nana's tortillas in Mesa today.

Tata was always served first, perhaps Sonoran enchiladas made with a recipe Nana took from her mother's birthplace in the Mexican border state of Sonora, albondigas (garlicky meatballs with mint) with calabacitas (squash with onions, chiles, and cheese), or pork chops alongside a relish of small hot yellow chile peppers, and, for dessert, the rich bread pudding capirotada. Then he would launch into "The Story of My Life", often the chapter that began in Easter week of 1922 at the annual fiesta at Guadalupe, a Yaqui village southwest of Mesa. Tata, by then a sign painter, had gone to watch the Yaqui dances and to drink moonshine. However much he drank, though, he never stopped noticing his surroundings; he had been orphaned, and an orphan is watchful, even when he becomes a man. On that day, he saw people digging into Mexican food sold at rickety stands. "I was fascinated," Tata would say, "by the throngs of people, mostly Anglos, who mobbed these huts. In those days, people thought Mexican food was dirty. But I had an idea: if tamales were selling like hotcakes from little huts, what would happen if you sold them in a clean, pretty place?"

He talked incessantly of his idea to Nana, who had by this time become an accomplished cook. And so, a year after he attended the festival, Tata and Nana and a few friends, armed with 600 tamales, set up at the Guadalupe fiesta. They wore their best clothes and immaculate, starched white aprons. They wrapped each tamale in a white paper napkin and charged ten cents apiece—double the going rate. "Part of my philosophy," Tata would explain, "was to impress our customers with the fact that the food was handled in the most sanitary ways." The tamales sold out, tripling my grandparents' initial investment. "It was the greatest night of my life," Tata liked to tell people. "My mind was racing with ideas: Mexican food in restaurants, Mexican food in grocery stores, Mexican food made in huge quantities by machine."

Tata had to wait more than 20 years for the one ingredient his plan lacked: capital. During those decades, his hair turned gray, while Nana's, initially reddish brown, turned black. But Tata was obsessed. He registered the company's original name, Rosita, in 1925. He had my uncle Adolfo draw a picture of a pretty Mexican girl for a logo. (The sultry señorita in the yellow sombrero adorns the label even now.) He invested in 10,000 tamale wrappers for his imaginary company. But 14 years passed before he found suitable partners: Ann Petrie, the owner of two Mesa restaurants, and R. G. Scarborough, a young accountant. In 1945, the partners hired a local woman to make tamales according to Nana's recipe in one of Petrie's kitchens. The enterprise grew quickly, in a short time requiring a move into a large, modern factory.

Soon, the company was making prepared tortillas, sauces, beans, and frozen foods. In the late 1950s, after a trademark squabble, its name was changed slightly, from Rosita to Rosarita. No matter. The foods took off in grocery stores, at first locally, then across the West. Nana was a consultant, contributing recipes and test-freezing food. She cooked big Mexican dinners when new partners needed persuading; once, she even cooked for Frank Lloyd Wright in Scottsdale. In 1961, Beatrice Foods, one of the era's biggest processed-food conglomerates, came knocking. My grandparents sold Rosarita; they never had to worry about money again. Today, ConAgra Foods owns the brand.

By the time I, the daughter of their son Pedro, who had moved to the East Coast, gained consciousness of things, in the '60s, Nana and Tata were traveling quite a bit, and she was driving a Mercedes. Whenever they came for a visit, we insisted that Nana cook. She was making tortillas in our house the day John F. Kennedy was shot; one tear fell on the stove and left a stain that could never be scrubbed away. Every year at Christmas we received a box of tamales from Nana and our aunts; each one had an olive in the middle, the prize in our pudding. Some summers, we'd go to Mesa, to the big adobe house Tata had begun building in 1929. Nana's daughters and granddaughters sat and talked while Nana crocheted afghans in lurid color combinations. (She never met a color she did not like.)

Tata held that no trip was complete without a visit to Rosarita land. So we would go, leaving Nana at home with her beloved telenovelas. At the factory, we watched men in rubber boots stir half-ton vats of refried beans. Though Tata and Nana were no longer in the business, their photo was on the wall and we were treated like V.I.P.'s. Then we would go home for lunch.

Tata died, the family at his bedside, at 93 in 1990. And then Nana died, her bed similarly encircled, four years later, at 96. Since then, other grandmothers have made flour tortillas for me, and they have been good, very good, but tortillas like my Nana's have gone with her to heaven—where she is no doubt making them for God and all the apostles, her rings safe in a teacup near the sink.