Soft, chewy Snickerdoodle Cookie Bars loaded with cinnamon-sugar flavor and the perfect crackly top. All the classic taste you love in an easy bar form—perfect for parties, potlucks, or cozy nights in!
Prepare a 9x13 baking dish with a light coating of butter or oil or line it with parchment paper.
Whisk the flour, cream of tartar, baking soda, and salt in a mixing bowl. Set aside.
Cream the butter, granulated sugar, and brown sugar together in the bowl of a stand mixer using the paddle or butter beater attachment, until the mixture is light and fluffy, about 2-3 minutes.
Beat in the eggs and vanilla.
Slowly add the dry ingredients, mixing until just until combined.
Transfer the dough to the prepared dish - spreading it into an even layer.
Mix the cinnamon and sugar together in a small bowl and then sprinkle it evenly over the top of the dough.
Bake for 25-30 minutes, or until the edges are set and a toothpick inserted in the center comes out clean.
Let cool completely in the pan before cutting into bars.