Preheat the oven to 375°F (190°C).
To make the crust: In a large bowl, mix together the flour, butter, sugar, and salt. Using your hands, work the ingredients together until the mixture resembles coarse crumbs. Add the water and mix until the dough comes together. Form the dough into a disk, wrap in plastic wrap, and refrigerate for 30 minutes.
Roll the dough out on a lightly floured surface until it is 1/8-inch thick. Place the dough into a 9-inch tart pan and press into the bottom and sides. Trim the edges and prick the bottom of the dough with a fork. Line the tart shell with parchment paper and fill with baking beans. Bake for 15 minutes. Remove the parchment paper and baking beans and bake for an additional 10 minutes.
Brush the tart shell with the melted butter. In a medium bowl, mix together the apples, sugar, cinnamon, and nutmeg. Fill the tart shell with the apple mixture. Bake for 25 minutes.
Remove the tart from the oven and let cool. Spread the cooled Vanilla Custard over the tart. Serve warm or at room temperature.