Preheat oven to 350 °
Add softened butter, vegetable oil, powdered sugar and granulated sugar to a mixing bowl.
Beat with electric mixer until light and fluffy.
Beat in eggs and vanilla.
Add flour, baking soda, salt and cream of tartar.
Mix until well combined.
Scoop into balls (I use a medium cookie scoop)
Roll in sugar and place on a lined baking sheet about 2 inches apart.
Smash with the bottom of a glass.
Bake for 12-14 minutes or until lightly browned around the edges.
Remove to a wire rack to cool.
Store in an airtight container up to 2 weeks.