1. Preheat oven to 425 degrees. Generously butter a 9-inch metal pie plate; set aside. Line a baking sheet with parchment paper, and set aside. On a lightly floured work surface, roll out the dough to a 9-inch round, about 1/4-inch thick. Place dough on the prepared baking sheet, and chill until firm, about 30 minutes.

2. Meanwhile, in a small saucepan, mix together the sugar, 2 tablespoons cold water, and the lemon juice to form a thick syrup. Bring to a boil over high heat, swirling pan; cook until the mixture turns medium amber, about 3 minutes. Remove the pan from heat, and pour the mixture onto the bottom of the prepared pie plate. Immediately add the butter, distributing evenly.

3. Arrange the apples, rounded sides down, around the bottom of the pan in a circular pattern, starting from the outside and working in, fitting them as close together as possible (the apples will be the top of the tart when served). Drape the chilled dough round over the apples to cover the mixture completely.

4. Bake until golden, about 25 minutes. Meanwhile, line a rimmed baking sheet with a clean nonstick baking mat. Remove the tart from the oven, and immediately invert onto the mat, working quickly but carefully to avoid contact with the hot caramel. Using tongs, carefully lift the pie plate off of the tart. Transfer the sheet to a wire rack to cool. Serve warm with creme fraiche, if using.