01 - Preheat a grill pan or large skillet over medium-high heat. Rub the steak on both sides with olive oil, chili powder, cumin, salt, and pepper.
02 - Place the seasoned steak in the hot pan and grill for 3 to 4 minutes per side for medium-rare, adjusting time to your preferred doneness. Transfer to a cutting board and let rest for 5 minutes before slicing thinly against the grain.
03 - In the same pan, add the sliced bell pepper, onion, and diced jalapeño. Sauté over medium-high heat until softened and lightly golden, about 5 minutes. Remove from heat and set aside.
04 - Lay each flour tortilla flat. On one half of each tortilla, layer the sliced steak, sautéed vegetables, and shredded cheese. Fold the other half of the tortilla over the filling to create a half-moon shape.
05 - Wipe the pan clean and return it to medium heat. Cook each assembled quesadilla for 2 to 3 minutes per side, pressing down gently with a spatula, until the tortilla is golden brown and the cheese is fully melted.
06 - Transfer each quesadilla to a cutting board and slice into wedges. Serve immediately with sour cream, salsa, chopped fresh cilantro, and lime wedges on the side.