Add pecans to a food processor and process until finely ground flour but not pecan butter.
Add pecan flour and baking blend to a skillet and toast over medium heat until golden and fragrant, about 4 minutes. Remove from pan and set aside to cool. Whisk in the glucomannan and salt, set aside.
Cream butter in a large bowl. Add in sweetener and continue to beat until light and fluffy. Add in vanilla extract and egg, beating until just combined.
With your mixer on low, add in half of the flour mixture, mixing until just incorporated, then mix in the rest.
Wrap cookie dough with cling wrap and refrigerate for at least an hour. Dough may be made several days ahead.
Line a baking tray with parchment paper. Divide dough into 20 balls. Place balls on the prepared baking tray.
Place baking sheet with cookies in the freezer for 15 minutes prior to baking. Preheat oven to 350 degrees.
Bake for 9-11 minutes. The cookies will be barely golden and still appear largely uncooked. Dust with a touch of powdered sweetener immediately (it will dissolve into the warm cookies).
Allow to cool completely before rolling in more powdered sweetener. Store in an airtight container for up to 1 week.
It does not take much sweetener for the powdered coating. Less is more with stevia based blends. I actually decided to use just ground xylitol for the powdered coating. It took less than 1/4 cup.