Step 1: Heat 1 tablespoon of oil in a large skillet over medium-high heat. Add the sliced onions and bell peppers, sautéing until softened and lightly caramelized (about 5-7 minutes). Remove from skillet and set aside.
Step 2: In the same skillet, increase heat to high. Add the thinly sliced steak in a single layer. Season with salt, pepper, and garlic powder. Sear for 2-3 minutes until browned and cooked through. Mix the vegetables back in.
Step 3: Wipe the skillet clean and melt 1/2 tablespoon of butter over medium heat. Place one tortilla in the skillet.
Step 4: Place one slice of provolone on half of the tortilla, top with a quarter of the steak mixture, and add another slice of provolone. Fold the tortilla over.
Step 5: Cook for 2-3 minutes per side until the tortilla is golden brown and the cheese is completely melted. Repeat with the remaining tortillas.
Step 6: Let the quesadillas rest for 1 minute before slicing into wedges and serving.