Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the softened unsalted butter and granulated sugar. Beat together until light and fluffy, about 2-3 minutes.
Add in the large egg and vanilla extract. Mix until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, cream of tartar, baking powder, baking soda, and salt. Gradually add to the wet ingredients, mixing on low speed until just combined.
Using a cookie scoop or spoon, drop tablespoons of dough onto a baking sheet lined with parchment paper.
Bake for 10-12 minutes, or until the edges are lightly golden.
Let the cookies cool on the baking sheet for about 5 minutes, then transfer them to a cooling rack.