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

In a small bowl, combine the diced apples, brown sugar, and cinnamon. Stir until apples are evenly coated and set aside.

In a large bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt.

In a separate bowl, whisk together the milk, eggs, melted butter, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix with a spatula until just combined. Do not overmix.

Spread half of the batter into the prepared loaf pan. Top with half of the apple-cinnamon mixture. Add the remaining batter, followed by the rest of the apple mixture. Use a knife to gently swirl once or twice.

Bake for 50-60 minutes, or until a wooden skewer inserted into the center comes out clean. Let the bread cool in the pan for 15 minutes before transferring to a wire rack to cool completely.

Once cooled, whisk together the powdered sugar, milk, and vanilla extract for the glaze. Drizzle it over the top of the bread before slicing and serving.