1. Preheat oven to 375℉
2. Combine chicken, 1 cup salsa, and sour cream in a large bowl. Spread ½ cup salsa on bottom of a 9-inch deep-dish pie plate.
3. Press 1 tortilla into pie plate; top with half the chicken mixture. Sprinkle with an even layer of cheese and half the spinach. Repeat, reserving about ¼ cup cheese. Top with final tortilla; spread with remaining ½ cup salsa and sprinkle with reserved cheese.
4. Cover with foil; bake 20 minutes. Remove foil and bake 5 more minutes, until cheese melts.
5. To serve, slice into wedges.