A comal is a cast iron griddle commonly used for cooking tortillas in Mexico. Like anything made of cast-iron, it must be cured and cared for in a particular manner. When you first acquire your comal, wash it well, then heat it on your stove. Pour on some vegetable oil, about 2 tablespoons, and spread the oil with a folded paper towel. Repeat the coatings about two or three times. Cool the comal, wipe off the excess oil, then store. Before each usage of your comal, coat it with oil once in the same manner. When cleaning your comal, never scrub the surface, or clean it with harsh chemicals. Usually, a light cleaning with a damp towel will suffice.
Comals are very versatile. I use mine to make pancakes and grilled cheese sandwiches. You can roast chilies on them as well. If you don't have a comal, a frying pan, or any other stovetop griddle will do.