Cream the butter and both sugars together on medium-high speed for 5 minutes or until the mix is pale and fluffy. Scrape down the bowl.
1 cup butter, 1 cup powdered sugar, 1 cup granulated sugar
Add eggs in, one at a time, mixing well after each one and scraping down the bowl.
1 cup butter
Pour in oil and vanilla. Mix on low until smooth. It might look a little curdled at first. Just keep mixing and it will come together.
1 cup neutral oil, 2 teaspoons vanilla
Mix in the flour, baking soda, cream of tartar, and salt on low until well combined. Scrape the sides and bottom of the bowl once or twice to ensure it is evenly mixed. The dough will be very soft.
4 ½ cups flour, 1 teaspoon baking soda, 1 teaspoon cream of tartar, 1 teaspoon salt
Place ½ cup sugar on a small plate.
Scoop with a 2 tablespoon size cookie scoop, roll into balls, and then roll in sugar. Place the dough balls on a parchment paper lined cookie sheet. Then use a flat measuring cup or glass cup to gently flatten the cookies to about ¾ inch thick or a little under.
Set in the refrigerator for at least 30 minutes before baking. If you are leaving it for longer, be sure to cover tightly with plastic wrap so the dough does not dry out.
About ten minutes before they are done chilling, preheat the oven to 325ºF.
Bake for 8-10 minutes. You want the edges to be dry and the middle to be puffy but not wet. The bottoms should just be starting to turn golden but none on the top. Cool for 5 minutes before transferring to a cooling rack to finish cooling.