Preheat the oven to 350°F (175°C) and prepare an 8 x 4 loaf pan with parchment paper and baking spray.

In a medium bowl, toss the chopped apples with brown sugar and 1 tablespoon of cinnamon, then set aside.

In another medium bowl, whisk together the flour, baking powder, and salt, then set aside.

In a large bowl, beat together the granulated sugar and butter until well combined.

Beat in the eggs one at a time, then add the milk and vanilla extract, mixing well.

Gradually add the flour mixture to the wet ingredients, stirring gently until just combined.

Pour half of the batter into the prepared loaf pan, then top with half of the apple mixture.

Spread the remaining batter over the top, then add the rest of the apple mixture on top.

Gently pat the apples into the batter and swirl them in with a butter knife 2 to 3 times.

Place the loaf in the oven and bake for 55-60 minutes, until a toothpick inserted in the center comes out clean.

Cover with foil during the last 15-20 minutes to prevent over-browning. Cool in the pan on a wire rack for about 10 minutes.

Lift the loaf from the pan using the parchment paper and let it cool completely on a wire rack.

In the meantime, whisk sour cream, vanilla extract, and powdered sugar together, adding milk until you reach a drizzling consistency.

Once the loaf is cooled, drizzle the icing over it before slicing and serving.