I eat this all the time...and it's very quick and easy!
All you need is:
*mozarella cheese (shredded)
*your favorite tomato sauce...I prefer Barilla Marinara Sauce
Put your oven on broil and set it to high. On a large cookie sheet, place two flour tortillas on it and place on the highest rack of your oven. Keep a close eye on it. When it starts to brown, remove the pan from the oven, remove the tortillas and wipe off the condensation from the pan.
Place one of the tortilla shells, browned side down, on the cookie sheet...place it back in the oven.
Watch it, and when it is brown, remove the pan from the oven and sprinkle cheese over the top. Put that back under the broiler until it starts to melt a little...remove the pan from the oven, sprinkle a little more cheese on it, and place the remaining tortilla shell on top, browned side down. Place once again under the broiler.
Meanwhile, heat up your sauce in the microwave.
When the top of the tortilla is brown, remove and cut into quarters.