01 - Preheat oven to 325°F. Position the rack in the center of the oven.
02 - Heat olive oil in a large skillet over medium heat. Add the sliced onions and minced garlic, sautéing until softened and fragrant, about 4 minutes.
03 - In a large mixing bowl, combine the sliced cabbage, grated carrots, sautéed onions and garlic, sauerkraut, caraway seeds, smoked paprika, black pepper, salt, and dill. Toss everything together until evenly distributed.
04 - Transfer the vegetable mixture to a large greased casserole dish, spreading it into an even layer. Pour the vegetable broth evenly over the top.
05 - Cover the dish tightly with aluminum foil or a fitted lid. Place in the oven and slow roast for 1 hour and 30 minutes.
06 - Remove the foil or lid and stir the casserole gently. If desired, sprinkle the grated Gruyère or Swiss cheese evenly over the top. Return to the oven uncovered for an additional 30 minutes, until the cabbage is caramelized and the cheese is bubbling and golden.
07 - Remove from the oven and let rest for 10 minutes. Serve warm, dolloped with sour cream if desired.