Place the butter in a medium pan and heat it over medium-low heat, stirring often. Cook until the butter turns foamy and golden brown, about 8 to 10 minutes. Be careful not to let it burn!
215 grams unsalted butter
Immediately pour 76 grams of browned butter into a bowl and refrigerate it for 1 hour. In a separate bowl, add 104 grams of browned butter and let it cool at room temperature for 20 minutes.
To the bowl with 104 grams of butter, add granulated sugar and brown sugar. Mix with an electric mixer or whisk for 1–2 minutes, until the mixture is lighter in color. Add the egg and vanilla extract, and mix until fully incorporated.
50 grams granulated sugar (1/4 cup), 90 grams brown sugar (1/2 cup), 1 large egg,, 1 teaspoon vanilla extract
In a separate bowl, whisk together the flour, cinnamon, cornstarch, cream of tartar, baking soda, baking powder, and salt. Gradually add the dry ingredients to the wet mixture. Mix until just combined.
180 grams all-purpose flour ( 1 cup + 1/4 cup), 1/4 teaspoon ground cinnamon, 1 tablespoon cornstarch, 1/2 teaspoon cream of tartar, 1/2 teaspoon baking soda, 1/4 teaspoon baking powder, 1/8 teaspoon salt
Line a plate or tray with parchment paper. Scoop out the dough into 8 even-sized balls and refrigerate them for 30 to 45 minutes.
Preheat your oven to 350°F (175°C). Place the chilled dough balls onto a baking sheet and bake for 10–12 minutes. Once baked, use a circular cookie cutter or glass to reshape them into perfect circles, if needed. Gently press the tops of the cookies with the bottom of a measuring cup to create a small dent for the frosting. Let the cookies cool completely on a wire rack.