Preheat the oven to 350°F and line an 8x8-inch baking pan with parchment paper. Set it aside for later.

In a large bowl, whisk together the melted butter and brown sugar until smooth. Add in the egg, extra yolk, and vanilla extract, mixing until fully combined.

In a separate bowl, stir together the flour, baking powder, and salt. Gently fold the dry mixture into the wet ingredients, stirring just until no streaks of flour remain—be careful not to overmix.

Spread the blondie batter evenly into the prepared baking pan. For the cinnamon swirl, mix the cinnamon and sugar in a small bowl. Drop generous spoonfuls of the cinnamon sugar mixture over the top of the batter. Using a butter knife, swirl the mixture throughout the top to create visible, marbled patterns.

Bake for 30 to 40 minutes, or until the edges are golden and set, and the center has risen but remains soft. The middle will still be a little underdone—that’s perfect, as it will continue baking slightly as it cools.

While the blondies cool, prepare the cream cheese glaze. In a small saucepan over medium-low heat, combine the cream cheese, heavy cream, powdered sugar, vanilla extract, and a pinch of salt. Whisk constantly until the mixture is smooth and everything has melted together. Remove from heat and let it cool slightly.

Once the blondies have cooled completely, drizzle the glaze over the top. Slice into 9 even squares and serve!