Begin by using a small melon baller to scoop out the top center portion of the onion (approximately 1/3 of the way down) to create a well in the middle. Position the onion on a sheet of aluminum foil and place the butter into the well. Combine the seasonings with the olive oil and pour this mixture over the butter into the well, allowing the oil and seasoning to flow down the sides of the onion. Season with salt and add any additional seasonings as desired.
Tightly seal the entire onion in the aluminum foil and place it inside a small baking dish or cast iron skillet to catch any oil that may escape from the foil.
After baking, remove the onion from the oven and carefully open the foil to check its doneness. The onion should be fork-tender, with the center jiggling slightly, and it should have a light caramelization. If it requires more time, simply reseal the foil and return it to the oven for another 10 minutes before checking again.
Set the oven to broil. Open the foil and drizzle more melted butter (or olive oil) along with an extra pinch of salt over the top. Broil for 5-10 minutes, keeping a close eye to prevent burning. This step will give the onion a beautifully golden brown, caramelized exterior.
Once done, peel away the outer layer and indulge in each layer underneath, adding an extra sprinkle of salt if desired. Be sure to pour all the juices from the foil over the onion when serving to enhance the flavor. This dish is delightful when paired with rice, crispy chickpeas, and other roasted vegetables such as crispy Brussels sprouts. Enjoy while hot!
