Instructions

• Preheat Oven: Heat the oven to 500°F (240°C, fan). Position a rack in the center of the oven for even heat distribution.
• Halve the onions or shallots lengthwise, discarding the papery skin and any tough or dry outer layers. Trim the top and bottom ends lightly, making sure the onion halves stay intact at the base.
• In a medium bowl, whisk together the melted butter, miso paste, and warm water until completely smooth and well combined.
• Arrange the onion halves, cut-side down, in a 9x13-inch (23x33 cm) high-sided baking dish or pan. Make sure they are spaced apart so that the sauce can evenly coat them.Pour the miso butter mixture over the onions, ensuring that the onions are partially submerged in the sauce.
• Cover the baking dish tightly with aluminum foil and bake for 35 minutes. The onions should begin to soften at this stage.
• After 35 minutes, remove the foil and carefully flip the onions so that they are cut-side up. Take care to keep the onions intact. Baste the onions generously with the sauce, using a spoon or baster. This will help them absorb the flavor and brown evenly.
• Return the onions to the oven, uncovered, and roast for an additional 45–50 minutes, basting every 10 minutes. The onions should become deeply browned and caramelized on top. The sauce will reduce to a gravy consistency.
• Carefully transfer the onions to a serving platter, pour the sauce over and around them, and serve immediately. The onions should be tender, with a rich, savory flavor from the miso and butter sauce.