In a large mixing bowl, beat together butter and sugar until fluffy. Then add eggs, milk and vanilla and beat until creamy.
In a different medium bowl, whisk together flour, cream of tartar, baking soda and salt.
Gradually add dry ingredients to butter mixture and beat until creamy.
Cover and chill dough for at least 30 minutes for best results.
Preheat oven to 350 degrees Fahrenheit.
Line baking sheets with parchment paper or silicone mat and set aside.
Combine sugar and cinnamon in a small bowl while oven is preheating.
Using a cookie dough scoop or Tablespoon scoop dough out and roll into a ball.
Place cookie dough ball into sugar and cinnamon mixture and roll to coat. Place on prepared baking sheet.
Place pan in preheated oven at 350 degrees Fahrenheit and bake for 8-101 minutes or until slightly set int he center for a soft cookie, bake longer if you want a crisp cookie.
Remove from oven and let cool for 2 minutes on baking sheet and then place onto wire rack to cool.
Store in airtight container.