Cream the butter and the granulated sugar until light and fluffy.
Beat in the eggs.
Next beat in the confectioner's sugar, vanilla, cream of tartar and salt.
Next beat in the oil and flour and beat until smooth and fluffy.
Cover and refrigerate the dough for 2 hours or until the dough is cold.
With a rounded tablespoon, roll the dough into cooky sized balls.
Place the balls 2 inches apart on lightly greased baking sheets.
Flatten the balls with the bottom of a glass that has been oiled and dipped in sugar.
Bake each baking sheet in a 350℉ oven for 8 to 10 minutes or until lightly browned.
Cool the cookies on wire racks.