TOP each tortilla with 1/4 cup cheese and 2 turkey slices; fold tortillas in half.
HEAT large nonstick skillet on medium heat. Add about 1-1/2 tsp. of the butter; heat until melted. Add 1 folded tortilla; cook 3 minutes on each side or until golden brown on both sides. Remove from skillet; cut into 6 wedges. Cover to keep warm. Repeat with remaining tortillas, adding remaining butter to skillet as needed.
MIX sour cream, chili powder and lime juice until well blended. Serve with the warm quesadillas.