Preheat your oven to 350°F (175°C) and line an 8x8 inch baking pan with parchment paper.

In a large mixing bowl, melt the unsalted butter. Stir in the light brown sugar and granulated white sugar.

Beat in the eggs one at a time until the batter is creamy.

Gradually sift in the all-purpose flour, baking powder, and cinnamon. Stir until just combined.

Pour half of the blondie batter into the prepared pan, spread evenly, and sprinkle with cinnamon sugar. Add remaining batter on top and swirl gently.

Bake in the preheated oven for 30 to 38 minutes until the edges are golden brown.

Cool in the pan for about 15 minutes before transferring to a wire rack.

Mix powdered sugar, cream cheese, and milk to create the frosting. Drizzle over completely cooled blondies.