Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking pan by greasing it with butter or lining it with parchment paper.

In a medium bowl, whisk together all-purpose flour, baking powder, baking soda, salt, and ground cinnamon until light and fluffy. Set aside.

In another large mixing bowl, combine melted unsalted butter and brown sugar until smooth. Add eggs and vanilla extract, whisking until creamy.

Gradually add the dry mixture to the wet ingredients, folding gently until incorporated. The batter should be thick and slightly lumpy.

Fold in diced apples until evenly distributed.

Pour the batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes or until edges turn golden brown.

While the blondies bake, whisk together powdered sugar, maple syrup, and melted unsalted butter in a small bowl until smooth.

Once baked, let the blondies cool for about 10 minutes before drizzling with the maple glaze.

Allow to cool completely in the pan before slicing into squares.