Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan.

In a medium bowl, toss the diced apples with brown sugar and ground cinnamon, letting the mixture sit for about 5 minutes.

In a large mixing bowl, cream together the butter and sugar until light and fluffy, then beat in the eggs one at a time, followed by vanilla.

Combine flour and baking powder separately, then alternate adding it and the milk to the creamed mixture.

Pour half of the batter into the loaf pan, sprinkle half of the apple mixture, then add the remaining batter and top with the remaining apples. Swirl gently.

Bake in the preheated oven for 50-55 minutes, checking for doneness with a toothpick.

Let the bread cool in the pan for about 10 minutes before transferring to a wire rack. Prepare the glaze by mixing powdered sugar, milk, and vanilla.

Drizzle the glaze over the cooled bread before serving.