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