Caramel Peach Snickerdoodle Bars

For the snickerdoodle bars:

• 1 1/2 cups (191 grams) all-purpose flour
• 1 teaspoon cream of tartar
• 3/4 teaspoon baking powder
• 1/4 teaspoon baking soda
• 1/4 teaspoon fine salt
• 1 teaspoon ground cinnamon
• 1 stick (113 grams) unsalted butter, at cool room temperature
• 2 ounces (57 grams) cream cheese, at room temperature
• 1/2 cup (100 grams) granulated sugar
• 1/4 cup (50 grams) light brown sugar
• 1 large egg plus 1 egg yolk, at cool room temperature
• 1 tablespoon milk
• 1 teaspoon vanilla extract

For the caramel peach topping:

• 1 tablespoon unsalted butter
• 3 cups (420 grams) peeled, pitted, and sliced peaches, from about 4 to 5 peaches (thaw if using frozen)
• 1/4 cup (50 grams) packed light brown sugar
• 1/4 cup (50 grams) granulated sugar
• 2 tablespoons all-purpose flour
• 1/2 teaspoon cornstarch
• 1/2 teaspoon cinnamon
• 1/2 teaspoon fine sea salt
• 1/2 teaspoon vanilla
• 2 tablespoons heavy cream