This pretty side dish (the onions open up like flowers) would be great alongside steak or roast chicken.
TEST-KITCHEN TIP:
This simple recipe has endless variations. Here are three to try: After they come out of the oven, top the onions with a little crumbled blue cheese, sprinkle a mixture of crumbled cooked bacon and grated Parmesan on top, or whisk a little Dijon mustard and garlic into the herb butter before starting.