In a medium frying pan, set to medium heat, add olive oil, onions and pepper. Saute for a couple minutes until onions are translucent. Add chopped flank steak, taco seasoning, cumin and cilantro and warm through. Remove the veggies and meat and place a flour tortilla in the pan. Sprinkle a fourth of the cheese across the entire tortilla, then place a fourth of the meat and veggie mixture on one half of the tortilla. Cook until the cheese bigins to melt and the tortilla browns slightly. Fold in half and remove, slicing the tortilla into wedges. Repeat with the other three tortillas.