Ingredients

• 2.75 cups all purpose (or measure-for-measure gluten free) flour
• 2 tsp cream of tartar
• 1 tsp baking soda
• 1/2 tsp kosher salt
• 1 cup salted butter (soft, not melted)
• 1/4 cup light brown sugar
• 2 large eggs
• 1 cup granulated sugar + 4 Tbsp for rolling
• 2 Tbsp ground cinnamon for rolling

Directions

• Preheat oven to 375.
• Mix dry ingredients: flour, cream of tartar, baking soda, salt
• In a separate bowl, use a mixer on medium-high to beat brown sugar, 1 cup granulated sugar and soft butter until fluffy. Scrape down sides and add one egg at a time, mixing further.
• Switch to medium-low and mix in the dry ingredients slowly.
• Mix cinnamon and remaining sugar.
• Form small balls and roll in the cinnamon and sugar. Bake well-spaced on parchment paper on baking sheets for 8-10 minutes, switching top and bottom halfway through, until just set and still soft. Let sit for a few minutes on the cookie sheet to finish setting before transferring.

Original source