Heat the oven to 350°F. Grease a 9 x 5-inch loaf pan, and line the bottom with parchment paper if desired.

Whisk the flour, baking powder, and salt together in a medium bowl. In a separate large bowl, beat the softened butter and granulated sugar until light and creamy.

Beat the eggs into the butter mixture one at a time, mixing after each addition. Stir in the vanilla extract.

Add the dry ingredients alternately with the milk, beginning and ending with the dry ingredients. Mix only until the batter is combined, taking care not to overmix.

In a small bowl, stir together the brown sugar, cinnamon, and the optional tablespoon of flour. The flour helps the cinnamon-sugar mixture bind slightly around the apples.

Spread about half of the batter in the prepared loaf pan. Add approximately half of the chopped apples and half of the brown-sugar mixture, then add the remaining batter.

Top the loaf with the remaining apples and cinnamon-sugar mixture. Swirl the top lightly with a knife, avoiding excessive swirling so the loaf keeps its distinct layers.

Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs. If the top browns too quickly, loosely cover it with foil during the final 15–20 minutes.

Cool the bread in the pan for about 15 minutes, then transfer it to a rack to cool further. Let it cool substantially before glazing and slicing so the crumb can set.

Whisk the confectioners’ sugar with 1–2 tablespoons of milk, adding the milk gradually until the glaze is pourable. Drizzle it over the cooled loaf before serving.