In a saucepan over medium heat, melt the butter, stirring constantly until it turns golden brown and develops a nutty aroma.

Remove the saucepan from heat and let the brown butter cool for about 10 minutes.

In a mixing bowl, whisk together the cooled brown butter and granulated sugar until smooth.

Beat in the eggs one at a time, mixing well after each addition.

In another bowl, whisk together the flour, cream of tartar, baking soda, cinnamon, and salt.

Gradually add the dry mixture to the wet ingredients, mixing until just combined.

Cover the dough and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C).

Scoop the chilled dough, roll it into balls, and roll each ball in the cinnamon-sugar mixture before placing them on a lined baking sheet.

Bake for 10-12 minutes until the edges are set but the centers remain soft.