Preheat your oven to 350°F (175°C). Grease and line an 8x8-inch (20x20cm) square baking pan with parchment paper, leaving some overhang for easy removal.

In a large mixing bowl, whisk together melted butter, light brown sugar, and granulated sugar until smooth.

Add the eggs, vanilla extract, and ground cinnamon, and whisk until fully combined.

In a separate bowl, sift together the all-purpose flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, stirring gently until a thick batter forms.

Spread the batter evenly into the prepared pan, smoothing the top with a spatula.

In a small bowl, mix the topping ingredients (2 tablespoons granulated sugar and 1 teaspoon ground cinnamon). Sprinkle this mixture evenly over the batter.

Bake in the preheated oven for 25-30 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out with a few moist crumbs.

Remove the blondies from the oven and let them cool completely in the pan on a wire rack.

Once cooled, use the parchment paper overhang to lift the blondies out of the pan. Slice into squares or rectangles and serve.