In a large pan that’s deep enough to accommodate the cabbage when raw, heat the olive oil. Add the onion and cook slowly over medium-low heat until the onion is golden brown (it’s okay if the edges start to crisp), 15 to 20 minutes. Add the cabbage and sauté, tossing with tongs, until it has collapsed slightly and is no longer stiff, about 2 minutes.
Raise the heat to high and add the allspice, nutmeg, and salt. Add pepper generously to taste (about 20 grinds) and stir to coat the cabbage with the spices. Add the wine and bring to a boil. Cover the pan, reduce the heat to medium low, and cook until the cabbage is almost tender and the wine is absorbed, about 40 minutes. Raise the heat to medium and add the vinegar, stirring to deglaze the pan. Add the brown sugar, stir, and cover again, reducing the heat to medium low. Continue to braise until the liquid is absorbed and the cabbage is very tender, about 30 minutes more. If the cabbage is done but there’s still liquid in the pan, raise the heat to medium high and cook, uncovered, until the liquid has reduced to a glaze. Toss to coat and transfer to a serving dish.