In a food processor, combine sugar, flour, pumpkin pie spice, baking powder and 1/2 teaspoon of salt and pulse just to combine.
Add both butters and pulse until all of the butter is incorporated into the flour and the mixture is sandy. Add the egg and vanilla and pulse until the mixture comes together in big clumps.
Turn the dough out onto a clean work surface and knead a few times to form a ball.
Divide the dough in half, pat into 2 discs about 1/4-inch thick, wrap in plastic wrap and refrigerate until firm, about 1 hour.
Position an oven rack in the middle of the oven and preheat to 350 degrees F. Line 2 baking sheets with parchment paper.
Put 1 disc of dough between 2 pieces of parchment paper and roll out the dough to 1/8-inch thick.
Cut out with thanksgiving cookie cutters and arrange on one of the prepared baking sheets about 2 inches apart.
Bake for 10 to 12 minutes.
Once cool enough to handle, transfer cookies to a rack to cool completely.