How to Make It
Preheat oven to 450°.
Combine cabbage, onion, oil, sugar, black pepper, and salt in a large bowl; toss to coat. (It's OK if the cubes start to separate.)
Divide cabbage mixture between 2 foil-lined jelly-roll pans. Bake at 450° for 20 minutes, stirring and rotating pans after 10 minutes.
In the same bowl that you used for the cabbage, combine apple, vinegar, mustard, and caraway seeds; toss to coat.
Remove cabbage from oven, and carefully transfer to the bowl with the apple. Add butter; toss gently to combine.
Heat broiler to high. Return cabbage mixture to pans, spreading evenly. Place each pan under the broiler for 3 minutes (this will be a two-phase operation) or until edges begin to brown and evenly crisp.