Start by preheating your oven to 350°F (175°C). Spray or line a 13x9 baking dish and set it aside.
In a medium saucepan, melt the butter over medium heat until it begins to brown. This adds a delicious, nutty flavor to the blondies. Once browned, let the butter cool for about 10 minutes.
Stir the apple butter and 1 cup of the brown sugar into the cooled butter. Add in the eggs and vanilla, mixing until well combined.
Now, stir in the flour, baking powder, 1 teaspoon of cinnamon, nutmeg, and salt. Mix just until everything is combined (don’t overmix!).
In a small bowl, toss the diced apples with the remaining ½ cup of brown sugar and the remaining teaspoon of cinnamon. This gives the apples that sweet, cinnamon-sugar goodness!
Spread the batter into your prepared baking dish, then sprinkle the cinnamon-sugar apples evenly over the top. Bake for about 30 minutes, or until the center is set and the edges are just starting to brown. Allow the blondies to cool before glazing.
While the blondies are baking, make the maple glaze. In a small saucepan, melt the butter over medium heat until it turns brown. Browning the butter gives the glaze a rich, toasty flavor.
Add the maple syrup, powdered sugar, cinnamon, and salt. Whisk everything together until smooth and well combined.
Drizzle the glaze over your cooled apple blondies and let it set before slicing and serving. It adds the perfect finishing touch to this already scrumptious dessert!