1. In a heavy 6- to 8-inch skillet, melt the 3 tablespoons of butter over moderate heat, add the onions and cook, stirring constantly, for 5 minutes, or until they are soft and transparent but not brown.
2. With a rubber spatula, transfer them to a large mixing bowl, and stir in the bread crumbs, parsley, 2 tablespoons of milk, anchovy fillets, lemon peel, sage, ¼ teaspoon of salt and a few grindings of pepper. Taste for seasoning and set aside.
3. Preheat the oven to 350°. Rub the bruised garlic over the bottom and sides of a shallow baking-and-serving dish just large enough to hold the fish comfortably. Then with a pastry brush or paper towel, coat the bottom of the dish with 1 tablespoon of the softened butter.
4. Wash the fish inside and out under cold running water, and dry it thoroughly with paper towels. Loosely fill the cavity of the fish with the stuffing, then close the opening with small skewers, crisscrossing them with kitchen cord as if lacing a turkey.
5. Brush the fish with the remaining tablespoon of softened butter and sprinkle it with salt and a few grindings of pepper. Place the fish in the baking dish, and pour in the combined wine and orange juice.
6. Bake uncovered in the middle of the oven for 30 to 40 minutes, basting every 10 minutes with the pan liquid. The fish is done when its flesh is firm to the touch. Serve at once directly from the baking dish, moistening each serving with a little of the sauce.
