1. Preheat the oven to 325F. Grease a 9x13-inch metal baking pan and line the bottom and sides of the pan with parchment paper.
2. Make the pecan blondies: in a large bowl, whisk together the flour, baking powder, cinnamon, baking soda and salt.
3. In a small saucepan, melt the butter and brown sugar over medium heat. Remove from the heat and let cool for 10 minutes at room temperature.
4. Whisk the eggs and vanilla into the butter mixture.
5. Make a well in the center of the flour mixture and add the butter mixture. Stir just until no dry streaks of flour remain (do not overmix).
6. Fold in the ground pecans.
7. Scoop the batter into the prepared pan and spread evenly. Cover the top with the pecans.
8. Bake until a wooden pick inserted into the center comes out clean, 20 to 22 minutes.
9. Let cool in the pan on a wire rack until it reaches room temperature.
10. Make the maple glaze: in a bowl, whisk together the maple syrup and powdered sugar until smooth.
11. Cut the blondies into 36 squares and drizzle with glaze.