Preheat oven to 425F. Mix together cilantro, scallions, salt, pepper, and spinach. (If using fresh, process these ingredients in a food processor) Coat an 8" square baking dish with nonstick spray. Layer 4 tortillas in baking dish (they overlap, it might help to cut them if you wish, but it doesn't matter). Layer half the beans, salsa, then spinach mixture, and cheese. Repeat with remaining ingredients, ending with cheese. Cover dish with foil, place on a rimmed baking sheet. Bake until bubbling (25-30 minutes). Remove foil and continue baking for about 15-20 minutes longer. Cool 5-10 minutes before serving.