Brown the Butter: In a medium saucepan over medium heat, melt the unsalted butter. Continue cooking while stirring frequently until the butter turns golden brown and has a nutty aroma, about 5-7 minutes. Remove from heat and let it cool slightly.
Mix Sugars: In a large mixing bowl, combine the brown butter, granulated sugar, and light brown sugar. Beat using an electric mixer on medium speed for about 2-3 minutes until well combined and fluffy.
Add Eggs and Vanilla: Add the eggs one at a time, mixing well after each addition. Then, add the vanilla extract and continue to mix until fully incorporated.
Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, cream of tartar, and salt.
Combine Mixtures: Gradually add the dry mixture to the wet mixture, mixing on low speed until just combined. Avoid over-mixing.
Chill Dough: Cover the bowl with plastic wrap and refrigerate the dough for at least 30 minutes (this helps prevent spreading during baking).
Prepare Rolling Mixture: In a small bowl, combine the ½ cup granulated sugar and 2 tablespoons of ground cinnamon. Mix well.
Preheat Oven: Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
Form Cookies: Using a cookie scoop or tablespoon, scoop out portions of dough and roll them into balls. Roll each ball in the cinnamon-sugar mixture until fully coated.
Place on Sheet: Place the rolled dough onto the prepared baking sheet, spaced about 2 inches apart.
Bake Cookies: Bake in the preheated oven for 10-12 minutes or until they are lightly golden around the edges but still soft in the center.
Cool Down: Remove from the oven and let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
Chilling the dough helps prevent spreading during baking.