With an electric mixer, beat butter for one minute. Add sugar and beat for one more minute until light.
Add starter and vanilla. Beat until well mixed.
Add salt and flour until just incorporated and the cookie dough holds together (sift the salt into the flour, or be sure to sprinkle evenly). Fold in pecans.
Refrigerate cookie dough for 15-30 minutes.
Preheat oven to 350° F (176° C).
Using a cookie scoop or your hands, make 1" balls and place 2-3 inches apart on cookie sheet.
Flatten each ball with the palm of your hand or the bottom of a glass, reshaping if necessary.
Bake for 20 minutes, or until the bottoms are golden brown. Transfer to wire rack.
Once cool, dust with confectioners' sugar.
To find the ideal temperature for your oven and this cookie, test one cookie before allowing the rest to cool. The inside should be soft but not gummy (it will cook a little more after you remove it from the oven).