In a small bowl, combine the chicken, sour cream and 3/4 cup salsa. Spread 1/4 cup salsa on the bottom of a greased 8-in. square baking dish., Layer with half of the tortillas and chicken mixture; sprinkle with half the tomatoes, minced cilantro and half of the cheese. Repeat layers with remaining tortillas, chicken mixture, tomatoes and cheese., Bake, uncovered, at 400° until bubbly, 20-25 minutes. Serve with remaining salsa and, if desired, optional toppings.