Preheat the oven to 425°. In a deep, 10-inch cast-iron skillet, add 1/3 cup granulated sugar, the pear nectar and pear slices. Sprinkle the pears with 1 tablespoon granulated sugar. Cook, undisturbed, over medium-high heat until the sugar caramelizes, about 10 minutes.
Meanwhile, using a blender, combine the half-and-half, eggs and vanilla. Add the flour, salt and remaining granulated sugar. Blend on high speed for 30 seconds, then scrape down the sides of the blender and blend for 10 seconds more.
Pour the batter over the pears and bake until lightly browned and puffy, about 15 minutes. Lower the heat to 350° and bake until a skewer inserted in the center comes out clean, about 10 minutes more.
Sprinkle with confectioners' sugar before serving.