Preheat the oven to 350F then spray a 10-inch skillet with nonstick cooking spray and set aside.
In a large bowl cream the butter and sugar until light and creamy. You can also use a stand mixer with a paddle attachment for this.
¾ cup butter, 1 cup granulated sugar
Add in the egg, egg yolk, and vanilla extract and mix to combine.
1 egg, 1 egg yolk, 2 teaspoon vanilla extract
Fold in the flour, cream of tartar, salt, cinnamon, and baking soda just until the flour mixture disappears.
2 & ¼ cup all purpose flour, 1 teaspoon salt, 1.5 teaspoon cream of tartar, ½ teaspoon baking soda, 1 & ½ teaspoon cinnamon
Spread the snickerdoodle cookie dough in the prepared skillet. Mix the 2 tablespoons of sugar with the 1 teaspoon of cinnamon in a small bowl. Sprinkle the cinnamon sugar mixture on top, and bake for 25 minutes. Allow the snickerdoodle skillet cookie to cool for 20-30 minutes before scooping some ice cream on top and enjoying it!
2 tablespoon granulated sugar, 1 teaspoon cinnamon