Nothing can beat the supple texture and earthy flavor of freshly pressed tortillas. Still, there are some commercial brands that are quite good, though you should always cook them before serving. Read the package: The chief ingredients should be corn, water, and slaked lime (sometimes listed as "corn treated with lime" or "trace of lime"). That last item is another name for calcium hydroxide, which is dissolved in a solution used to soak the corn before grinding—this makes the corn more digestible and improves the flavor and texture of the tortilla—a process called nixtamalization. Superior packaged tortillas are available in the United States in Mexican grocery stores and in many supermarkets; they can also be obtained by mail order.