Position the racks in the upper and lower thirds of the oven and preheat the oven to 325°F (convection) or 350°F (standard). Line two sheet pans with Silpats or parchment paper.
Toss the flour and pecans together in a medium bowl.
Place the butter in the bowl of a stand mixer fitted with the paddle attachment and mix on medium-low speed until smooth.
Add the 90 grams/3/4 cup plus 1 3/4 teaspoons powdered sugar and mix for about 2 minutes, until fluffy. Scrape down the sides and bottom of the bowl.
Add the flour mixture and mix on low speed for about 30 seconds, until just combined. Scrape the bottom of the bowl to incorporate any dry ingredients that have settled there.
Divide the dough into 30-gram/1 1/2-tablespoon portions, roll into balls, and arrange on the sheet pans, leaving about 1 1/2 inches between them. Press the cookies into 2-inch disks.
Bake until pale golden brown, 15 to 18 minutes if using a convection oven, 22 to 25 minutes if using a standard oven, reversing the positions of the pans halfway through. (Sandies baked in a convection oven will not spread as much as those baked in a standard oven and will have a more even color.)
Set the pans on a cooling rack and cool for 5 to 10 minutes. Using a metal spatula, transfer the cookies to the rack to cool completely.
If desired, dust with powdered sugar.
The cookies can be stored in a covered container for up to 3 days.
