Heat olive oil in a skillet over medium-high heat. Add the steak and onion and season with salt and pepper. Cook, stirring occasionally, until steak is cooked through and onion is softened, about 8 minutes.
Melt butter in a separate skillet over medium heat. Place one tortilla in the skillet and sprinkle with half of the cheese. Top with half of the steak and onion mixture, then sprinkle with remaining cheese. Top with a second tortilla and cook until cheese is melted and the tortillas are lightly browned, about 4 minutes per side.
Remove quesadilla from the skillet and let cool slightly. Repeat with remaining ingredients.
Cut each quesadilla into 6 wedges and sprinkle with parsley. Serve warm.
Interesting Facts
The name "Philly Cheesesteak" is derived from the city of Philadelphia, where the sandwich is said to have originated.
The classic Philly Cheesesteak consists of thinly sliced steak, melted cheese, and onions on a soft hoagie roll.
Quesadillas are a traditional Mexican dish consisting of a tortilla filled with cheese and other ingredients.