Dry the steak with kitchen towel then chop the steak into thin slices. Add the steak to a small bowl then season with salt, black pepper, garlic powder, chilli powder, ancho chilli flakes and paprika. Add in the coriander, olive oil and lime juice then mix the seasonings into the steak. Set the bowl aside.
Place a large frying pan on a medium to high heat and add the sunflower oil. Once heated, add in the fajita vegetables and cook for 2 minutes. Remove the vegetables from the pan and add them to a plate then set aside.
To the same pan, add in the steak and cook for 2 minutes while stirring. Add the vegetables back into the pan and mix with the steak. Remove the steak and veggies from the pan then set aside.
Reduce the heat to low then place a tortilla in the pan. After 1 minute, turn the tortilla onto the other side and sprinkle ¼ of the cheese onto half the tortilla. Top the cheese with half the meat and vegetables then top the meat and veggies with another ¼ of the cheese. Fold the tortilla and press down with a spatula. .
Cook for 1 - 2 minutes until slightly browned then carefully flip the quesadilla onto the other side and cook for another 1 - 2 minutes or until the cheese melts. Remove from the pan and repeat the process for the other quesadilla. Cut each quesadilla in half or thirds and serve with sour cream, guacamole, salsa or hot sauce.