How to Make Chewy Snickerdoodle Bars

• In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar for 3 to 4 minutes until light and fluffy.
  1 Cup Unsalted Butter, 1 ½ Cups Granulated Sugar, ½ Cup Light Brown Sugar
• Add the eggs, extra egg yolk, and vanilla extract. Beat for another 3 to 4 minutes until the mixture looks pale and fluffy, almost like whipped frosting.
  2 Large Eggs, 1 Large Egg Yolk, 1 Tablespoon Vanilla Extract
• In a separate bowl, whisk together the flour, cream of tartar, baking soda, and salt.
  1 Teaspoon Salt, 2 ¾ Cups All-Purpose Flour, 2 Teaspoon Cream of Tartar, 1 Teaspoon Baking Soda
• Gently fold the dry ingredients into the wet mixture using a spatula or clean hands. Mix only until the flour streaks disappear. Avoid overmixing to keep the bars tender.
• Line your baking pan with parchment paper. Spread the dough evenly into the pan, using a small piece of parchment paper to press the dough smooth.
• Combine the sugar and cinnamon, then sprinkle the entire mixture evenly over the dough. Gently press it into the surface.
  ¼ Cup Granulated Sugar, 1 Tablespoon Ground Cinnamon
• Bake in a preheated 350°F oven for 25 to 30 minutes. The edges should be puffed and lightly golden, and the center should appear just set.
• Do not overbake. If the bars look completely done in the oven, they may become dry after cooling.
• Allow the bars to cool in the hot pan for at least 30 minutes. This carryover cooking helps create the soft, chewy center.