Preheat your oven to 350°F (175°C). Line a 9x13-inch metal baking pan with parchment paper, leaving a 1-inch overhang on the sides for easy lifting later.

Blot the pumpkin: Measure out ½ cup pumpkin puree onto a plate lined with 4 layers of paper towels. Press gently with additional towels to absorb excess liquid until the puree reduces slightly in volume. This is the secret to chewy, non-cakey bars!

In a large mixing bowl, whisk together melted butter, dark brown sugar, and granulated sugar until glossy and smooth. Whisk in the blotted pumpkin puree, whole egg, egg yolk, and vanilla extract until completely emulsified.

In a medium bowl, whisk together all-purpose flour, cream of tartar, baking soda, ground cinnamon, ginger, nutmeg, and sea salt. Fold the dry ingredients into the wet mixture with a spatula just until a soft, thick cookie dough forms. Spread evenly into the prepared pan, smoothing the surface.

In a small bowl, stir together the 3 tablespoons granulated sugar and 1 ½ teaspoons cinnamon. Evenly shower the entire cinnamon-sugar mixture over the surface of the batter.

Bake at 350°F (175°C) for 24 to 28 minutes, until the edges are golden and set and a toothpick inserted into the center comes out clean with just a few moist crumbs. Do not overbake!

Transfer pan to a wire rack and let cool completely in the pan for at least 1 hour. If using glaze, whisk cream cheese, powdered sugar, milk, and vanilla until silky, then drizzle generously across the cooled bars. Slice into 16 thick squares and enjoy!