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

In a small bowl, mix together the brown sugar and ground cinnamon. Set aside.

In another bowl, combine the diced apples with 2 tablespoons of the brown sugar-cinnamon mixture. Toss until the apples are well coated. Set aside.

In a large bowl, beat the granulated sugar and softened butter together until smooth and creamy. Beat in the eggs, one at a time, then stir in the vanilla extract.

Whisk together the flour and baking powder in a separate bowl.

Gradually mix the dry ingredients into the creamed mixture, alternating with the milk, until just combined.

Pour half of the batter into the prepared loaf pan. Add half of the apple mixture over the batter, then sprinkle half of the remaining brown sugar-cinnamon mixture on top.

Pour the remaining batter over the apple layer and top with the remaining apple mixture, followed by the remaining brown sugar-cinnamon mixture.

Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center of the loaf comes out clean.

While the bread is cooling, mix the powdered sugar, milk (or cream), and vanilla extract (if using) in a bowl until smooth. If the glaze is too thick, add a little more milk until it reaches a drizzling consistency.

Once the bread has cooled, drizzle the glaze over the top. Allow the glaze to set before slicing and serving.