Preheat oven to 350 degrees. Grease and flour a 9 x 5-inch loaf pan and set aside. Mix the brown sugar and cinnamon together in a bowl and set aside. In a stand mixer, combine the white sugar and butter until smooth. Add the eggs and vanilla and continue to beat on medium speed until combined. Add flour and baking powder, then finally, add the milk.
Pour half of the batter into the prepared pan and cover with the chopped apples. Pat the apples into the batter with the back of a spoon. Sprinkle with half of the sugar and cinnamon mixture. Pour the remaining batter over apple layer; top with remaining apples and add more brown sugar/cinnamon mixture.
Bake for 50 minutes or until toothpick inserted in the middle of the loaf comes out clean. Cool in pan 10 minutes before transferring to a cooling rack.