Step 1: Heat 1 tablespoon of olive oil or butter in a large skillet or griddle over medium heat. Add the sliced onions and bell peppers. Sauté for 5-7 minutes, or until they are softened and lightly caramelized. Season lightly with salt and pepper. Remove the veggies from the skillet and set aside.
Step 2: Increase the heat to medium-high. If needed, add another tablespoon of oil or butter to the same skillet. Add the thinly sliced steak in a single layer. Cook for 2-3 minutes, stirring occasionally, until the steak is browned and cooked through. Avoid overcrowding the pan. Season the steak with garlic powder, onion powder, and a pinch of salt and pepper.
Step 3: Reduce the heat to medium-low. Place one flour tortilla in the clean skillet. Sprinkle half of your shredded cheese blend evenly over one half of the tortilla.
Step 4: On top of the cheese, evenly distribute half of the cooked steak and half of the sautéed onions and peppers over the same half of the tortilla.
Step 5: Sprinkle the remaining half of the cheese over the steak and veggie mixture.
Step 6: Fold the empty half of the tortilla over the filling. Cook for 3-4 minutes per side, or until the tortilla is golden brown and crispy, and the cheese is completely melted and gooey. Gently press down with a spatula. Repeat with the remaining ingredients for a second quesadilla.
Step 7: Once cooked, carefully transfer the quesadilla to a cutting board. Let it rest for a minute before slicing into wedges. Serve hot.