Heat olive oil or butter in a skillet over medium heat. Sauté onions and peppers for 5–7 minutes until soft and lightly caramelized.,Add thinly sliced beef to the skillet. Cook for 2–3 minutes until browned. Season with salt, pepper, and optional garlic powder. Remove from heat.,Wipe out skillet and place over medium heat. Place one tortilla in the skillet.,Sprinkle cheese on half the tortilla, add the steak mixture, then top with more cheese. Fold the tortilla in half.,Cook 2–3 minutes per side until the tortilla is golden and cheese is melted.,Transfer to a cutting board, let cool slightly, then slice into wedges. Serve warm with your choice of dipping sauce.