Preparation

• Position a rack in the center of the oven and heat the oven to 350°F. In a medium bowl, whisk the flour, baking soda, salt, and cream of tartar to blend. Using a stand mixer with the paddle attachment, beat the butter and 1-1/2 cups of the sugar on medium speed until light and fluffy, about 3 minutes. Scrape the bowl with a rubber spatula. Beat in the eggs until thoroughly combined, about 2 minutes. Scrape the bowl again. With the mixer on low speed, slowly blend in the flour until incorporated, about 30 seconds.
• In a small bowl, mix the cinnamon and remaining 1/4  cup sugar. Drop the dough by rounded tablespoonfuls into the cinnamon sugar and roll around to coat. Set the coated balls of dough about 3 inches apart on greased cookie sheets. Bake until golden brown on the edges and slightly soft in the center, 15 to 18 minutes. Let the cookies cool on the sheet for 1 minute before transferring them to a rack to cool.

Make Ahead Tips

The cookies can be stored in an airtight container for up to three days or frozen for a month.