1. In a medium bowl, sift flour and baking powder; set aside.
2. Pulse pecans, confectioners' sugar, salt, and pumpkin pie spice in a food processor until finely ground (but not wet); transfer to the bowl of an electric mixer fitted with the paddle attachment.
3. Add butter and granulated sugar; mix on medium speed until fluffy. Add in vanilla and egg. Reduce speed to low. Slowly add flour mixture; mixing until combined.
4. Divide the dough in half and shape into disks. Wrap disks in plastic wrap and refrigerate until firm, at least 2 hours.
5. Preheat oven to 375 degrees. Line a baking sheet with parchment paper or a silicone mat.
6. Working with 1 disk at a time, roll out dough on a lightly floured surface to 1/8 inch thick. Refrigerate 20 minutes. Cut out circles with a 2-inch fluted cutter. Cut out centers of half the circles with a 1/2-inch cutter; reroll scraps.
7. Space 2 inches apart on parchment-lined baking sheets. Bake squares and hearts until pale golden, 8 to 10 minutes. Transfer to racks to cool.
8. Sprinkle cutout cookies with confectioners' sugar. Spread Biscoff Spread onto uncut circles; top with cutout ones.
Notes
- Store in an airtight container up to 2 days.- You can find the Linzer cookie cutters on Amazon.Adapted from Martha Stewart