Preheat oven to 425°F. Brush 1 side of 4 tortillas evenly with 1 tablespoon melted butter, and place, buttered side down, on 2 baking sheets. Divide turkey, Caramelized Onions and Red Peppers, and cheese slices evenly among tortillas on baking sheet; top with remaining tortillas. Brush with remaining 1 tablespoon melted butter.
Bake in preheated oven until golden brown and cheese begins to melt, 12 to 15 minutes. Gently press quesadillas with a spatula; cut into wedges, and sprinkle with cilantro. Serve immediately with Easy Guacamole and sour cream.