Preheat oven to 350°F. Grease an 8 x 4-inch non-stick loaf pan. If desired, cut a sheet of parchment to fit the bottom and sides of the loaf pan allowing for a 2-inch overhang on either side. This will enable the loaf to be lifted after it's baked.

In a medium bowl combine the apples, brown sugar, and cinnamon. Allow the fruit and sugar mixture to macerate for 15 minutes. In another medium bowl sift together the flour, baking powder, and salt.

In a large separate mixing bowl, combine the granulated sugar and butter until light. Beat in eggs, one at a time. Beat in milk and vanilla. Add flour mixture; stir just until combined.

Pour half of the batter into the prepared loaf pan. Add half of the apple mixture. Spread remaining batter over the apples in pan. Top with remaining apple mixture. Use a table knife to swirl apples into batter in a serpentine ribbon pattern. This action will yield a swirl effect when the slices of bread are cut.

Bake about 1 hour or until a toothpick inserted in the center comes out clean. Cool in pan on a wire rack 10 minutes. Remove from pan and cool completely on a wire rack. Drizzle with sour cream glaze before slicing and serving.

In a small bowl combine 3 tablespoons of sour cream, ½ teaspoon of vanilla, and ¾ cup powdered sugar. If the mixture appears too dense, add milk 1 teaspoon at a time, until you achieve drizzling consistency.