In a bowl, combine olive oil, lime juice, chili powder, cumin, garlic powder, salt, and black pepper. Add the flank steak and marinate for at least 15 minutes.

Heat a grill or grill pan over medium-high heat. Cook the steak for about 4-5 minutes per side or until desired doneness. Remove from heat and let rest.

In a skillet, add a little olive oil and sauté the sliced bell peppers and onions over medium heat until softened, about 5-7 minutes.

Slice the cooked steak into thin strips. On half of each tortilla, layer cheese, sautéed vegetables, and steak. Fold the tortilla over to create a half-moon shape.

In the same skillet, cook the quesadillas over medium heat until the tortillas are golden brown and the cheese is melted, about 3-4 minutes per side.

Cut the quesadillas into wedges and serve with salsa, guacamole, or sour cream.