Preheat oven to 350°F.
In the bowl of a stand mixer, combine butter, granulated sugar, confectioners sugar and mix until just combined.
Drizzle in oil and pour in eggs and mix well.
In a bowl add the cream of tartar and salt to the flour and roughly sift.
Slowly add the flour to the butter mixer and allow the mixer to combine until the dough pulls away from the sides of the mixer bowl.
Using an ice cream/cookie scoop, scoop out golf-ball size portions on a parchment lined cookie sheet.
Roll out each cookie dough ball until it is smooth and round.
Using a kitchen glass that has been pressed into granulated sugar, press down on each cookie dough ball until the center of the cookie is pressed flatter than the edges. Repeat this on all cookies.
Bake for 7-9 minutes or until edges are just slightly starting to brown and the center no longer appears wet. (Do not overbake! It can result in a crisp cookie that does not taste as good.)