Preheat oven to 350 degrees. Lightly grease a 9 x 13 inch baking pan. (I tried lining the pan with parchment paper, but as the dough is quite thick, that really didn’t work. I ended up scraping it all off the paper and making a big mess!)
In a medium bowl, whisk together the flour, baking powder and salt. Set aside.
In a large mixing bowl, beat together the butter, brown sugar, eggs and vanilla until smooth. Add the flour mixture to the egg mixture and beat until well blended.
Spread the batter evenly in the prepared pan.
In a small bowl, combine the white sugar and cinnamon.
Sprinkle the mixture evenly over the batter in the baking pan.
Bake for 20-25 minutes or until the surface springs back when gently pressed. Remove from oven and let cool slightly on a wire rack. While still warm, cut into squares with a sharp knife…or cut into shapes using a metal cookie cutter.