How to Make It
Preheat the oven to 500°. Butter one side of a 12-inch round of parchment paper. In a large skillet, melt the 1/2 stick of butter. Add the radishes and greens along with 3 tablespoons of water and season with kosher salt and pepper. Top with the parchment paper, buttered side down, and cook over moderate heat, shaking the pan occasionally, until the radishes are just tender, about 15 minutes.
Meanwhile, butter a large rimmed baking sheet. Arrange the orange slices in a slightly overlapping layer, then top with the halibut, skin side down. Pour the wine over the fish and season with kosher salt and pepper. Roast the fish for 12 to 14 minutes, until just opaque throughout. Cut into 8 fillets and discard the skin.
Transfer the fish, roasted oranges and any pan juices to a platter. Drizzle with olive oil and sprinkle with sea salt. Serve with the radishes and orange wedges.