How to Make It
In a large, deep skillet, heat the olive oil until shimmering. Add the cabbage wedges cut side down and cook over moderate heat, turning once, until browned, 6 to 8 minutes total. Transfer to a plate.
Add the bacon to the skillet and cook over moderate heat, stirring occasionally, until rendered but not crisp, about 5 minutes. Add the onion and a generous pinch of salt and cook, stirring occasionally, until softened and just starting to brown, about 10 minutes. Stir in the vinegar and simmer over moderately high heat until reduced by half, about 3 minutes. Add the cider and bring to a boil. Nestle the cabbage wedges in the skillet, cover and braise over moderately low heat, turning once, until tender, about 20 minutes. Using a slotted spoon or spatula, transfer the cabbage to a platter and tent with foil.
Boil the sauce over moderately high heat, stirring occasionally, until slightly thickened, about 5 minutes. Remove the skillet from the heat and swirl in the butter. Season the sauce with salt and pepper; spoon over the braised cabbage and serve.