Heat oven to 425°. Place butternut squash, cut slice down on a parchment line baking sheet. Bake squash until soft, 40 to 45 minutes. Decrease oven to 350 degrees. When the squash is cool enough to handle, scoop the flesh out into a medium bowl; add salt, and mash with a fork.
Meanwhile, slice apples into ⅛-inch-thick wedges and place in a medium bowl. Add lemon juice and toss to combine.
In a medium skillet, melt 3 tablespoons butter over medium-high heat. Add 2 tablespoons brown sugar and cook, stirring, until sugar dissolves. Cook apple slices in the butter and sugar in 3 or 4 batches, until golden and caramelized, about 1 minute on each side. As they finish cooking, transfer to a plate and set aside. Wipe down skillet.
In the skillet, melt 3 tablespoons butter over high heat. Add 2 tablespoons brown sugar and cook until sugar dissolves. Stir in 4 tablespoons cream and the brandy and cook until slightly thickened, about 1 minute. Remove from heat and add to the squash, mixing well to combine. Transfer squash mixture to a buttered 3-quart ovenproof casserole. Arrange apple slices over squash; set aside. Wipe down skillet.
In the skillet, melt remaining 3 tablespoons butter over medium heat. Add remaining 2 tablespoons brown sugar and cook until dissolved. Add remaining 2 tablespoons of cream and cook, stirring, for 30 seconds. Stir in orange juice and cook for 1 to 2 minutes, until thickened and dark brown. Pour over the apples and cover with aluminum foil.
Bake for 15 minutes, remove foil and bake for another 15 minutes. Remove from oven and serve immediately, or let stand at room temperature for up to 30 minutes before serving.
