Pictured here is a traditional clay comal. The clay comal is a bit harder to find than the steel or cast iron versions. All types work well for heating tortillas.
You can use this comal over a gas flame. They are no recommended for use on a electric element because the heat is too intense and they may crack.
Like many foods in Mexico the filings for Tacos de Cazuela will vary depending on regional specialties. Rick Bayless, in Authentic Mexican describes some of these specialties. Many of the fillings are prepared in large clay dishes called cazuelas. The clay pots impart a traditional earthy flavor to the food.
Set everything out on the table and each person assembles his own tacos. Set out refried beans (frijoles refritos) Keep your fillings in warmed bowl.