Broiled Halibut with Orange- Shallot Butter Sauce

Preheat the grill. In a medium saucepan, melt 1 tablespoon butter over medium heat. Add the shallots and 1/2 tsp salt and cook, stirring, until softened, about 3 minutes. Pour in the orange juice and vinegar and bring to a boil. Cook until thickened and the consistency of syrup, about 5 minutes. Remove from heat.In a shallow baking dish, lay the fish flat side down; sprinkle with the remaining 1/4 teaspoon salt and pepper. Bake for about 6 minutes, until the fish is completely cooked through. Transfer the fish to a platter and keep it warm.Bring the remaining orange-shallot mixture to a boil over medium-high heat. Gradually add the remaining 7 tablespoons of butter, whisking slowly until it is absorbed and warmed through, about 5 minutes. Pour the sauce over the fish and serve. Garnish with orange slices.