In areas near Mexico City, cheese can be, and usually is, omitted, its place being taken by any of a variety of foods.
The Quesadilla vs. The Taco
The differences between a taco and a quesadilla consist of shape, kinds of filling and the order of filling and cooking.
A taco is rolled around the filling, while a quesadilla is flat, sandwiching its filling.
Quesadilla fillings are usually based on cheese (hence its name, from the Spanish queso), and are generally of a pasty consistency and considered appetizers. Taco fillings are usually based on meat or animal products, with a chunky consistency, and considered an entree.
Quesadillas are filled and cooked afterwards, tacos are a still-pliable tortilla wrapped around its filling. The usual case where tacos are cooked after filling is when making a flauta (Spanish for "flute," because of its shape). See taco for an explanation of taco shells.
Quesadillas are cut into strips in restaurants outside of Mexico, where they are served as an appetizer. In authentic Mexican restaurants, and in people's homes, quesadillas are generally eaten whole, and two to four of these often constitute a light meal.
Drop in a tortilla.
Drop on it shredded cheese (typically Monterey Jack Cheese), and any of the following:
Slice into strips and serve with any of those optional ingredients on top, or with a dipping sauce.Border Style Quesadilla Recipe
Preheat a frying pan, seasoned with oil, to simmering.
Cover with another tortilla, simmer until the cheese binds the two tortillas together and the outside starts to brown, flip it over, simmer a little longer.