Preheat your oven to 350°F (175°C). Grease an 8x8-inch baking pan or line it with parchment paper for easy removal.

In a large mixing bowl, combine the melted butter and brown sugar. Stir until well blended. Next, add the eggs one at a time, mixing well after each addition, followed by the vanilla extract.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add the dry mixture to the wet ingredients, stirring until just combined. Be careful not to overmix!

Gently fold in the diced apples, ensuring they are evenly distributed.

Spread the batter evenly in the prepared baking pan, smoothing the top with a spatula.

Place in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

While the blondies are baking, whisk together the maple syrup and powdered sugar in a small bowl until smooth.

Once the blondies are done baking, allow them to cool for about 10 minutes before pouring the glaze over the warm blondies. Let them cool completely before cutting into squares.