Spray frying pans with cooking oil and heat for 1 minute on medium.
Set aside 2 tbsp of cheese.
Place one tortilla in frying pan and spread remaining cheese on it. Sprinkle tomatoes, onions, mushrooms, peppers and remaining cheese.
Press down with spatula to help melt cheese. Top with second tortilla.
Carefully turn over and cook for about 1 minute, cut into four pieces.
Serve with sour cream, guacamole or your favorite salsa.