To Prepare the Pastry Dough:
In a food processor, combine flour and salt. Pulse in butter until incorporated and mixture resembles clumpy wet sand. Add egg and water and process until a dough forms. Pat dough into a disk, wrap, and refrigerate until ready to use.
To Make the Tart:
Heat oven to 425°. Combine potatoes, onion, turmeric, masala, olive oil, and salt and pepper to taste on a large rimmed baking sheet. Roast until tender and beginning to brown, about 20 minutes, tossing occasionally. Let cool while preparing the pastry.
On a lightly floured work surface, roll dough into a 13-inch circle. Transfer dough to an 11-inch tart pan and press to fit. Use a fork to prick holes all around the bottom of the crust and up the sides. Line with parchment, fill with dried beans or pie weights, and place on a baking sheet. Bake until golden, about 17 minutes. Reduce oven to 350°.
Combine potato mixture with bacon and parsley. With tart still on baking sheet, layer half of potato mixture into crust, top with cheese and then remaining potatoes. Whisk together half-and-half, eggs, and rosemary. Season with salt and pepper and pour over potatoes. Bake on lowest oven rack until set, about 35 minutes. Let rest 15 minutes before serving.