Generations of Tex-Mex lovers have etched their signatures into the front door at The Don’Key in Pasadena. Inside, waitresses in gaudy dresses—the place revels in colorful kitsch—pile gooey spoonfuls of cumin-scented queso flameado into hot, fresh tortillas, and proudly dispense platters of “Sabroso,” a house specialty of deep-fried flour tortillas topped with juicy chunks of fajita meat, queso, and shredded cheese.