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

Mix diced apples with brown sugar and ground cinnamon in a bowl. Set aside.

Cream together butter and granulated sugar until light and fluffy. Add eggs one at a time, then vanilla extract.

In another bowl, whisk flour and baking powder, then fold into creamed mixture alternately with milk.

Pour half of the batter into the pan, layer with half of the apple mixture, top with remaining batter and apples, then swirl with a knife.

Bake for 50-55 minutes until golden brown and a toothpick comes out clean.

Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Whisk together powdered sugar, additional milk, and vanilla extract for the glaze.

Once cooled, drizzle glaze over the bread before slicing and serving.