Begin by preheating your oven to 350°F (175°C). Prepare a 9x13 inch baking pan by greasing it lightly or lining it with parchment paper to facilitate easy removal later.
In a large mixing bowl, pour in the melted butter. Add in the packed brown sugar and granulated sugar. Using a whisk or a hand mixer, blend the ingredients well until the mixture is smooth and creamy.
Crack the eggs into the bowl and add the vanilla extract. Stir the mixture until the eggs are fully incorporated and the mixture is well combined.
In a separate bowl, sift together the all-purpose flour, baking powder, ground cinnamon, salt, and baking soda. This will help to aerate the mixture and ensure an even distribution of dry ingredients.
Gradually add the dry ingredient mixture to the wet ingredients. Use a spatula or wooden spoon to fold them together gently until just combined. Be careful not to overmix, as this can lead to dense blondies.
If you choose to include white chocolate chips, gently fold them into the batter, distributing them evenly without overworking the dough.
Pour the batter into your prepared baking pan. Use a spatula to spread it out evenly, ensuring all corners are filled.
Bake in the preheated oven for 20-25 minutes. The blondies are ready when the top is lightly golden and a toothpick inserted in the center comes out clean or with a few moist crumbs.
Once baked, remove the blondies from the oven and let them cool in the pan for about 10 minutes. After that, transfer them to a wire rack to cool completely, which will make cutting into squares easier.
Notes
For an elegant finishing touch, lightly dust the cooled blondies with cinnamon sugar before serving.