Preheat your oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper.

In a medium bowl, combine the all-purpose flour, cream of tartar, baking soda, ground cinnamon, nutmeg, cloves, and salt. Whisk until fully blended.

In a large mixing bowl, melt the unsalted butter and mix in the granulated and brown sugars until smooth and fluffy.

Add the pumpkin puree, egg, egg yolk, and vanilla extract to the butter-sugar mixture and mix until combined.

Gradually add the dry mixture to the wet mixture, stirring gently until just combined.

Spread the blondie batter evenly into the prepared baking pan.

Sprinkle the cinnamon sugar over the top of the batter.

Bake in the preheated oven for 30-35 minutes until edges are golden and a toothpick comes out with a few moist crumbs.

Let the blondies cool completely in the pan for about 30 minutes before cutting into squares.