When a recipe calls for cornmeal, it is usually referring to a slightly coarse and sandy flour made from ground, dried corn. It’s perfect for cornbread (for instance) and is widely used in other types of cooking, but in Mexico, Central and South America, this coarse type of cornmeal is not popular and a different type is used: masa harina.
Masa harina is a very finely ground corn flour made from corn that has been dried, cooked, ground up and dried again. The cooking water always contains slaked lime, also known as “limewater,” which gives masa harina its distinctive taste. It has a soft texture and reconstitutes very easily with water, so it is ideal for making easy-to-shape doughs.
When masa harina is mixed with water and a dough forms, it is generally just called masa (spanish for “dough”), and although the masa harina can be reconstituted with many other liquids – from water to eggs to oil – water is generally the most common. The most widely seen use of masa is in making corn tortillas. To make them, masa is simply mixed with water and salt, then mixture is rolled out and steamed or fried. Other uses for masa include empanadas, tamales, pupusas (an El Salvadorian specialty), arepas (small stuffed breads popular in Colombia and Venezuela).