Heat the oven to 425°F (200°C fan). Line a baking sheet with parchment paper.
Heat a large nonstick frying pan on high heat until very hot. Toss the onions with 2 tablespoons of the olive oil and 1/4 teaspoon salt and place them, cut-side down and spread apart, in the hot pan. Place a saucepan on top to weight the onions down and create an even char, then decrease the heat to medium-high and cook, undisturbed, for about 6 minutes, or until the cut sides are deeply charred. Transfer the onions to the prepared baking sheet, charred-side up, and bake for about 20 minutes, or until softened. (If your onions are larger than golf ball–size, this may take longer.) Set aside to cool.
Meanwhile, put the pomegranate juice into a medium saucepan on medium-high heat. Bring to a boil, then simmer for about 12 minutes, or until the liquid has reduced to about 5 tablespoons (75 milliliters) and is the consistency of a loose maple syrup. Set aside to cool; it will thicken as it sits.
Combine the chives with the remaining 3 tablespoons olive oil and a good pinch of salt and set aside.
Pour the pomegranate syrup onto a large platter with a lip and swirl it around to cover most of the plate. Use your hands to loosely separate the onions into individual petals, then place them haphazardly over the syrup. Dot with the goat cheese, if using, then spoon on the chive oil and finish with the Urfa chile flakes before serving.