Toss cornflakes in butter, sprinkle half into a 13x9x2 in baking dish. Layer the cabbage, onion, red pepper flakes, salt and pepper.
In a bowl, combine soup, milk, and mayonnaise until smooth. Spoon over cabbage mixture. Sprinkle cheese and remaining cornflakes mixture on top. Bake, uncovered, in preheated oven at 350 degrees F 45-50 minutes or until golden brown.