Preheat oven: Set to 325°F (165°C). Line baking sheets with parchment paper or use ungreased sheets.
Cream the fats and sugars:
In a large bowl, cream together the softened butter, vegetable oil, 1 cup granulated sugar, and 1 cup sifted confectioner’s sugar until smooth and fluffy.
Add eggs and vanilla:
Beat in the eggs one at a time, then stir in the vanilla extract until well blended.
Mix dry ingredients:
In a separate bowl, whisk together the flour, baking soda, cream of tartar, and salt. Gradually stir into the wet mixture until just combined.
Stir in pecans:
Fold in the chopped pecans until evenly distributed throughout the dough.
Shape the cookies:
Roll dough into 1-inch balls. Roll each ball in the additional 1/2 cup of sugar to coat.
Bake:
Place cookies 2 inches apart on ungreased baking sheets. Bake for 10–12 minutes, or until the edges are lightly golden.
Cool:
Let cookies rest on the baking sheet for a few minutes, then transfer to a wire rack to cool completely.
