Preheat your oven to 350°F (175°C). Line a large baking sheet with parchment paper. Place your Turbinado sugar in a small bowl so it's ready for rolling later.
In a medium bowl, gently hand-whisk together the All Purpose flour, bread flour, cream of tartar, baking soda, and salt. Set this bowl aside.
Using a stand mixer (or large bowl), beat the butter on medium-high speed until smooth and fluffy, about 1–2 minutes. Gradually add the granulated sugar, mixing thoroughly until the mixture is pale and light. Adding the sugar slowly helps prevent it from flying out of the bowl.
Add the egg, vanilla extract, and optional cake batter flavoring to the butter mixture. Beat for another minute until fully combined and smooth. Scrape down the sides of the bowl.
Pour the reserved dry ingredients into the wet mixture. Mix on low speed just until the flour disappears.
Important Note: Do not overmix once the flour is added to ensure the cookies stay tender.
Using a 1.5 tbsp scoop (approx. #40 scoop), portion the dough into 16 balls. Roll each ball generously in the Turbinado sugar until fully coated.
Arrange the dough balls on the baking sheet, spaced about 2 inches apart. Bake for 9–11 minutes.
Let them cool on the baking sheet for at least 5 minutes, no matter how tempting they are to eat.
The addition of bread flour and cream of tartar is what gives these cookies their signature soft, velvety interior. If you don't have cake batter extract/flavoring, you can omit it, but it adds a depth of flavor that mimics commercial bakery cookies. You can also use butter extract for a different delicious flavor profile.
*Percent Daily Values are based on a 2,000 calorie diet.
**Nutritional values are estimates based on available data and may vary depending on specific brands or preparation methods used.