In a large bowl, combine the chicken, cheese and RAGÚ® sauce. Mix to combine.
Spread the mixture evenly over the 4 tortillas.
Add 1/2 tablespoon of the butter to a large skillet and heat over medium high heat.
Place one of the filled tortillas in the skillet and cook for 3 - 5 minutes, until golden.
Fold to form the quesadilla, cut into triangles and serve with additional RAGÚ® sauce. Repeat to cook the remaining queadillas.