Preheat and Prepare Pan:

Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with parchment paper for easy removal.

Prepare the Apple Filling:

In a small bowl, toss the diced apples with sugar and cinnamon. Set aside.

Make the Batter:

In a large bowl, cream together the softened butter and sugar until light and fluffy. Beat in the eggs one at a time, then add the vanilla extract.

Combine Dry and Wet Ingredients:

In a separate bowl, whisk together the flour and baking powder. Gradually add the dry ingredients to the wet mixture, alternating with the milk, starting and ending with the dry ingredients. Mix until just combined.

Assemble the Bread:

Spread half of the batter into the prepared loaf pan. Layer half of the apple mixture on top, then sprinkle half of the cinnamon swirl mixture. Repeat with the remaining batter, apples, and cinnamon swirl. Use a knife to gently swirl the layers together.

Bake:

Bake the bread for 50–60 minutes, or until a toothpick inserted into the center comes out clean. Allow the bread to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.

Prepare the Glaze:

In a small bowl, whisk together the powdered sugar and milk until smooth. Drizzle over the cooled bread.