Whisk flour, baking powder, cinnamon, and salt in a medium bowl. Whisk brown sugar into butter in a medium bowl then add eggs and vanilla together and combine. Whisk in dry ingredients until just combined. Fold in Almond Rocca pieces or stir-in of your choice. Pour batter into prepared pan. Bake until blondies are just set, about 25 minutes. Remove from oven and let cool for 5 minutes. Using the edges of the parchment paper, pull blondies from pan, set on wire rack, and cool to room temperature. Cut into squares and serve.