In a medium saucepan, melt 1 cup of butter over medium heat, stirring continuously until browned.

In a mixing bowl, whisk together the browned butter and sugars until smooth. Incorporate 2 eggs one at a time.

Gradually add flour, baking powder, salt, and cinnamon, mixing gently until just combined.

Carefully fold in 2 cups of chopped apples, ensuring even distribution without overmixing.

Preheat oven to 350°F (175°C). Spread batter in a lined 9x13-inch baking pan and bake for 30–35 minutes.

Remove from the oven and let cool for 30 minutes. Prepare icing by combining brown butter, powdered sugar, and milk.

Drizzle icing over cooled blondies and slice into squares.