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 until softened and lightly golden, about 5 minutes. Remove from heat and set aside.
03 - Lay out the flour tortillas flat. On one half of each tortilla, layer the 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 has fully melted.
05 - Transfer the quesadillas to a cutting board and slice each into wedges. Serve immediately with sour cream, salsa, chopped cilantro, and lime wedges.