Preheat your oven to 350°F (175°C) and grease a 9×13 inch baking pan.
In a large bowl, cream together the butter, 1 cup of granulated sugar, and brown sugar until light and fluffy.
Add in the eggs one at a time, beating well after each addition, then mix in the vanilla extract.
In another bowl, whisk together the flour, cream of tartar, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Press half of the cookie dough into the prepared baking pan, spreading it evenly.
In a separate bowl, beat the cream cheese, sour cream, 1/2 cup of granulated sugar, egg, and vanilla extract until smooth.
Spread the cheesecake mixture over the cookie dough layer in the pan.
Drop spoonfuls of the remaining cookie dough over the cheesecake layer, gently spreading it to cover as much as possible.
In a small bowl, mix together the remaining 1/2 cup of granulated sugar and the cinnamon.
Sprinkle the cinnamon-sugar mixture evenly over the top layer of cookie dough.
Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and the center is set.
Allow the bars to cool completely in the pan before cutting into squares.
Variations & Tips
For a nutty twist, add a handful of chopped pecans or walnuts to the cookie dough. If you prefer a more pronounced cinnamon flavor, increase the cinnamon in the topping to 3 teaspoons. For a festive touch, consider adding a pinch of nutmeg or cloves to the cookie dough. These bars can also be made gluten-free by using a 1:1 gluten-free flour blend in place of the all-purpose flour.
