Heat the oven to 350°F.  Season the fish with black pepper. Place the fish into a 2-quart shallow baking dish. Drizzle with the olive oil.Bake for 15 minutes or until the fish flakes easily when tested with a fork.Grate 1 teaspoon zest and squeeze 1 tablespoon juice from 1 orange.  Cut the remaining orange into thin slices.Heat the broth, vinegar, cornstarch, orange juice, orange zest and brown sugar in a 2-quart saucepan over medium-high heat to a boil. Cook and stir until the mixture boils and thickens.Serve the fish with the citrus sauce. Garnish with the orange slices.