Add flour, butter and salt into a food processor. Pulse the machine on and off until the mixture is crumbly. With the machine running, slowly add the water until just combined (do not over-mix). Wrap the dough in plastic wrap and press flat into a disc. Chill for at least 2 hours or overnight.
Allow the dough the rest at room temperature for 5 minutes. On a lightly floured surface, roll the dough to approximately 1/4-inch thin. Carefully place the dough into a shallow 9x2-inch pie pan. Place the pan back in the refrigerator and chill for 30 minutes.
Preheat the oven to 400 degrees F. Place the tart pan on a baking sheet. Use a fork to poke holes throughout the bottom of the dough to prevent air bubbles from forming. Line the pie pan with foil and cover with uncooked beans. Bake the dough for 20 minutes, removing the beans and foil for the last 5 minutes. Allow to cool while preparing the other ingredients.
Prepare the acorn squash puree:
Line a baking sheet with aluminum foil.
Using a very sharp knife, slice the acorn squash in half. Scoop out and discard the seeds and membranes. Spread the softened butter generously onto the inside of the squash. Place the acorn squash cut-side down on the prepared sheet and roast at 400 degrees F until soft, approximately 50 minutes.
Once the squash is cool enough to be handled, scoop the pulp into a food processor and puree, discarding the skins. Reserve 2 cups of puree for the pie.
Prepare the pie:
Preheat the oven to 350 degrees F.
In a large bowl, vigorously whisk together the eggs until frothy. Whisk in the brown sugar until smooth, followed by the salt, pumpkin pie spice, acorn squash puree, half & half, and brandy.
Place the prepared pie crust on a baking sheet. Pour the filling into the crust and bake until the inside is just barely jiggling, 50-60 minutes. Allow to cool completely before serving.
Acorn squash puree and tart dough can be made up to 48 hours in advance. Store-bought refrigerator pie dough may be substituted