Heat the olive oil in a large non-stick skillet over medium heat. Add the diced bell peppers and red onions to the pan. Sauté the vegetables for about 3 to 4 minutes until they become soft and slightly translucent.

Add your shredded or diced cooked chicken to the skillet with the vegetables. Sprinkle the taco seasoning over the mixture and toss well to coat. If the mixture seems too dry, add a splash of water or lime juice. Stir for 1 to 2 minutes until the chicken is warmed through, then remove from skillet and set aside.

Wipe the skillet clean and return it to medium-low heat. Melt a small amount of butter in the pan.

Lay one flour tortilla flat in the skillet. Sprinkle a generous quarter-cup of cheese over the entire surface of the tortilla. Spread a portion of the chicken and vegetable mixture over only one half of the tortilla.

Once the cheese begins to melt, fold the empty side of the tortilla over the filling to create a half-moon shape. Press down gently with a spatula to help the layers stick together. Cook for 2 to 3 minutes per side until golden brown and crispy.

Transfer the finished quesadillas to a cutting board. Let them rest for one minute, then slice into triangles and garnish with fresh cilantro.