To make pesto, put cilantro and garlic in a food processor and process until finely chopped. With machine on, gradually add olive oil. Season and blend in cheese. Slice enough onion to equal about 1/2 cup.
Sauté with margarine in a small cast-iron skillet over medium-high heat. Cook past translucent stage until browned, about six to eight minutes. Prepare about 2 cups of vegetables -- the combination depends on personal taste.
Cook all vegetables except mushrooms in lemon juice and 2 tablespoons of pesto over medium to medium-high heat. When almost at al-dente stage, add sliced mushrooms. Continue cooking for about one minute. (The remaining pesto can be refrigerated for future use.) Place vegetable mixture over sizzling onions, then spoon vegetable-onion mixture into center of warmed tortillas. Top with condiments, to taste, then roll up tortillas. Three tortillas make one very generous portion.