Cream Butter and Sugar: In a large mixing bowl, beat 1 cup of softened butter with 1 ½ cups of granulated sugar until light and fluffy.
Add Eggs and Vanilla: Beat in 2 large eggs and 1 teaspoon of vanilla extract until well combined.
Mix Dry Ingredients: In a separate bowl, whisk together 2 ¾ cups of all-purpose flour, 1 teaspoon cream of tartar, ½ teaspoon baking soda, and ½ teaspoon salt.
Combine: Gradually add the dry ingredients to the wet mixture. Mix until just combined, being careful not to overmix.
Spread the Dough in the Pan
Prepare the Pan: Grease or line a 9x13-inch baking pan with parchment paper.
Spread the Dough: Evenly press the dough into the prepared pan using a spatula or lightly dampened hands.
Add the Cinnamon Sugar Topping
Mix Topping: In a small bowl, combine 2 tablespoons of granulated sugar with 2 teaspoons of ground cinnamon.
Sprinkle: Evenly sprinkle the cinnamon sugar mixture over the top of the dough.
Bake
Preheat Oven: Preheat your oven to 350°F (175°C).
Bake: Bake for 20–25 minutes, or until the edges are golden and the centre is set. A toothpick inserted in the middle should come out clean.
Cool: Let the bars cool completely in the pan before slicing into squares or rectangles.