Heat the butter or oil in a large pot and saute the onions and garlic until the onions are almost clear. Add the potatoes, sweet potatoes, and carrots, and saute over low heat until barely tender. Add enough apple cider to cover the vegetables halfway. Stir in maple syrup, tomato paste, and dill. Season with salt and pepper to taste. Simmer, covered, for 10 minutes. Add the broccoli and cauliflower and simmer 15 to 20 minutes longer, or until the vegetables are tender but not mushy.