9 small and medium yellow onions
1/4 cup olive oil
2 tablespoons unsalted butter, thinly sliced
coarse sea salt
fresh cracked black pepper
fresh rosemary sprigs

Place a rack in the upper third of the oven and preheat oven to 375 degrees F. Cut the tops off of each onion, but leave most of the skins on the onion. Arrange the onions in a square baking dish or a rimmed sheet pan. Drizzle the olive oil over the onions. Place a thin pat of butter on each onion. Sprinkle generously with salt and pepper and top with a rosemary sprig. Bake for 25 minutes until bubbling and tender. Increase the oven temperature to 400 degrees F and cook for another 15 to 20 minutes until the onions are completely tender and the tops are browned. Remove from the oven and allow to cool slightly. Remove the skins, slice and enjoy warm.