Preheat oven to 350 degrees F. Line baking sheets with parchment paper or a Silpat baking mat and set aside.

In a large bowl, whisk together flour, cream of tartar, baking soda, and salt. Set aside.

Using a mixer, beat the butter and sugar together until creamy and smooth, about 3 minutes. Add in the eggs and vanilla extract and mix until combined. Slowly add in the dry ingredients, with the mixer on low.

 Shape dough into balls, using about 1 tablespoon of dough. Mix 1/4 cup sugar and the cinnamon together in a small bowl. Roll balls in cinnamon-sugar mixture. Place 2 inches apart on prepared baking sheets. Bake 8 to 10 minutes or until set around the edges and centers are still soft. Do not overbake! Remove from oven and let cookies set up on baking sheet for 2 minutes. Transfer cookies to a wire cooling rack and cool completely.

While the cookies are cooling, melt the white chocolate chips in a microwave safe bowl. Dip cookies half-way into the white chocolate. Place cookies on wax paper or parchment paper. If desired, combine sugar and cinnamon together and sprinkle the mixture over the white chocolate. Let cookies set up until chocolate is completely dry.

Note-cookies will keep in an airtight container for 3-4 days.