Preheat the oven to 350°F (175°C). Grease or line a 9x9 baking pan with parchment paper.
In a large mixing bowl, cream together softened butter and brown sugar until smooth and fluffy.
Add eggs and vanilla extract, mixing until fully incorporated.
In a separate bowl, whisk together flour, baking powder, salt, and cinnamon.
Gradually fold the dry ingredients into the wet ingredients until just combined.
Spread the batter evenly into the prepared baking pan.
In a small bowl, mix together granulated sugar and cinnamon for the topping, then sprinkle evenly over the blondie batter.
Bake for 20-25 minutes, or until a toothpick comes out clean.
Allow the blondies to cool in the pan for 10 minutes before transferring to a cooling rack to finish cooling.
