Add a little oil to a frying pan, and fry the steak on medium-high for about three minutes per side or until it is cooked, medium rare. Set the steak aside to let it rest.
While the steak is resting, wipe out the frying pan, add a Tablespoon or two of oil, and fry the onion and pepper over medium heat until the onions are softened but not browned. Remove onion and pepper from the pan.
Slice the cooked steak into thin strips, cutting across the grain of the meat.
The quesadilla can either be folded in half as the cheese melts or it can be made with two smaller tortillas with the layer of cheese between them. Stacked tortillas can be a little tricky to flip, especially if the cheese has not melted enough to stick the tortillas together.
Heat the frying pan to medium high and place a tortilla in the pan. Spread about ½ cup of cheese over ½ of the tortilla. Spread 1/3 of the meat and 1/3 of the onions and peppers on top of the cheese, and use a spatula to fold the empty half of the tortilla onto the ‘loaded’ side. Press gently on the folded tortilla so it stays folded. Flip the quesadilla over and cook on the other side. Your quesadilla is done when the cheese is completely melted and the tortilla is getting crispy.
Cut each quesadilla into three wedges and serve with Mexican Crema or sour cream, fresh cilantro, sliced avocado or guacamole, a salsa of your choice, and lime wedges. Once again, be creative and use your favorite ingredients.