Chicken, onion and bell pepper sautéed together, spread over a tortilla with cheese and browned in a dry skillet. Thirty-five minutes, four servings, and the lid is what melts the cheese.
The skillet stays dry. There is no oil in the pan for this stage: the tortilla toasts against the metal and any fat added makes it greasy instead of crisp. The tablespoon of olive oil in the list is for the chicken and vegetables at the start. Cover it. A lid traps the heat above the quesadilla so the cheese melts at the same time as the bottom tortilla browns, and without it you get a burnt base and cold cheese in the middle. Let the filling cool slightly before it goes on the tortilla, which is what the third step is asking for. Hot filling steams the tortilla from the inside and softens it. Cheese is what holds a quesadilla together, so it needs to go right out to the edges. If it stops short, the two tortillas separate the moment you cut it.