1. Preheat oven to 350 degrees. On a lightly floured surface, roll out dough to a 1/8-inch-thick round. Fit into a 9-by-2-inch round fluted tart pan with a removable bottom. Line with parchment, and fill shell with pie weights or dried beans. Bake for 12 minutes. Remove beans and parchment, and bake until golden brown, about 25 minutes. Let cool completely in pan on a wire rack.

2. With the tip of a paring knife, scrape seeds from vanilla bean into a saucepan, and add pod. Add cream and milk, and bring to a simmer. Remove pan from heat, and cover. Let stand for 10 minutes.

3. Whisk together yolks and granulated sugar in a large bowl until pale and thick, about 2 minutes. Still whisking, add warm cream mixture in a slow, steady stream. Add arrowroot and nutmeg. Whisk until smooth. Strain through a fine sieve into cooled crust. Skim foam from surface.

4. Bake until edges of filling are set but center is still slightly wobbly, about 40 minutes. Let cool completely in pan on a wire rack. Refrigerate for at least 4 hours (or overnight). Before serving, unmold, sprinkle with nutmeg, and dust with confectioners' sugar.