Preheat oven to 350°F (175°C) and grease a 9×5-inch loaf pan with nonstick spray.
In a small bowl, mix brown sugar and cinnamon. Set aside.
Toss chopped apples with 2 tablespoons of granulated sugar and set aside.
In a large bowl, cream butter and remaining granulated sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
In a separate bowl, whisk together flour, baking powder, and salt.
Gradually add dry ingredients to the wet mixture, alternating with milk, beginning and ending with dry ingredients. Mix until just combined.
Spread half of the batter into the prepared loaf pan.
Sprinkle half of the cinnamon sugar mixture over the batter, then layer half of the apples.
Repeat layers with remaining batter, cinnamon sugar, and apples.
Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
Mix powdered sugar with a little milk to create a glaze and drizzle over cooled bread.
Slice and serve.