This is my absolute favorite cookie EVER! This recipe is from my grandmother's collection and it's been in my family forever. She told me that she's been using this recipe since the 1930's when she was 10. The cream of tartar is really the key ingredient that gives Snickerdoodles their signature tang, and what makes them not just sugar cookies with cinnamon! There are many Snickerdoodle recipes that don't call for cream of tartar, but those aren't classic Snickerdoodles. Some recipes use shortening instead of butter, but real butter gives them such a wonderful flavor!
Preheat oven to 400 degrees. ( I wait until my dough is almost done chilling to do this.)
Cream softened butter & sugar in large bowl (until light & fluffy); then beat in eggs (one at a time) and vanilla until well combined.
Combine flour, cream of tartar, baking soda, & salt in a separate bowl & whisk together.
Blend dry ingredients into butter mixture, slowly mixing in a little bit at a time. The dough will be a bit sticky.
Chill dough in fridge for 30 minutes at least. For best results, chill for longer. A few hours is great, 1 day is even better if possible! (I like to make my dough the night before, the cookies come out amazingly delicious when I do this) But even if u can only chill dough for 30 minutes, the cookies will still be great.
While dough is chilling, mix together the 4 tbsp. of sugar and 4 tsp. of cinnamon in a bowl. This measurement is a starting point, you may need more. Lots of cinnamon is important!
Shape dough into balls a bit bigger than a walnut and then roll them in the cinnamon & sugar mixture, making sure they are *VERY generously* coated on all sides.
Place 2 inches apart on ungreased cookie sheet and bake at 400 for 7-9 min. It is *very important* not to overbake these, even more so than with any other cookies I've baked. Keep checking them often. This isn't a cookie that should brown (although they look brown from the cinnamon, so it can be tricky to tell sometimes). They should be golden brown on the edges only. The bottoms should not be very browned either, just a light golden color. These cookies will puff up a lot while baking and then flatten out a bit with crinkley tops. They're so cute!
Sprinkle each cookie with a little more of the cinnamon & sugar mixture as soon as u take them out of the oven. Then remove from cookie sheet *immediately* & place them on a flat surface atop waxed paper. Store cookies in airtight container as soon as they're cooled.