Preheat the oven to 425 degrees.

Butter the bottom of a cast iron skillet with the softened butter. Arrange the apple slices in a concentric circle, overlapping slightly. Sprinkle with the cinnamon and drizzle with melted butter. Cover the pan with foil and roast in the oven for 25-30 minutes or until the apples are tender.

Place the sugar and water in a heavy saucepan and cook over medium heat, stirring just until the sugar melts. Once the sugar has melted, do not stir any longer. Cook for about 8 minutes or until the sugar is the color of an old penny. Gently swirl the pan occasionally to ensure even caramelization. Carefully add the cream and whisk until smooth. Remove from the heat and whisk in the butter and salt. Let cool slightly, then drizzle over the apples and serve. Top with whipped cream or ice cream, if desired.