01 - Preheat a grill pan or skillet over medium-high heat. Rub the steak with olive oil, chili powder, cumin, salt, and pepper. Grill for 3–4 minutes per side for medium-rare, or until desired doneness. Transfer to a cutting board and rest for 5 minutes, then slice thinly against the grain.
02 - In the same pan, add the sliced bell pepper, onion, and jalapeño. Sauté over medium-high heat until softened and lightly golden, about 5 minutes. Remove from heat and set aside.
03 - Lay each flour tortilla flat. On one half, layer sliced steak, sautéed vegetables, and shredded cheese. Fold the tortilla in half to enclose the filling.
04 - Wipe the pan clean and return to medium heat. Cook each quesadilla for 2–3 minutes per side, pressing gently with a spatula, until the tortilla is golden brown and the cheese is fully melted.
05 - Transfer quesadillas to a cutting board and cut into wedges. Serve immediately with sour cream, salsa, chopped cilantro, and lime wedges.