You can cook the onions up to one day ahead. Just before serving time, rewarm them in the oven while the roast rests.
This recipe is an accompaniment for Black Pepper-Crusted Standing Rib Roast au Jus.
Recipe information
Yield
Makes 8 servings
Ingredients
Preparation
Position 1 rack in bottom third and 1 rack in top third of oven and preheat to 450°F. Line 2 large baking sheets with foil; butter foil generously. Arrange onion wedges cut side down on prepared sheets. Brush onions with melted butter. Mix thyme, salt, and pepper in small bowl; sprinkle over onions. Drizzle with vinegar. Cover baking sheets tightly with foil. Roast onions 20 minutes. Reverse baking sheets from top to bottom and continue to roast until bottoms of onion wedges are brown, about 20 minutes longer. Remove foil. Using spatula, turn onion wedges over; cover with foil and roast until bottoms of onions are brown and edges are slightly crisp, reversing position of baking sheets after 5 minutes, about 15 minutes total. (Can be prepared 1 day ahead. Refrigerate onions on sheets, covered. Rewarm uncovered in 350°F oven until heated through, about 15 minutes.)
