Preheat the oven to 350°F.
Grease the loaf pan with cooking spray or butter. Set aside.
Peel, core, and finely chop the 3 apples. Set aside.
In a small bowl, add ½ cup dark brown sugar and 1 Tablespoon of apple pie spice mix. Set aside.
In a large mixing bowl, add 2 eggs and ½ cup granulated sugar and mix on low speed for 1 minute.
Next, add in the ½ cup of melted butter, ½ cup buttermilk, and ½ teaspoon vanilla extract. Mix on low speed for 1 minute until well combined.
Add in 1 ¾ cup flour, 1 teaspoon baking powder, ½ teaspoon baking soda, remaining ½ teaspoon apple pie spice, and ¼ teaspoon salt.
Mix on low speed for 1 minute.
Gently fold in the chopped apples into the batter.
Add half of the batter to the loaf pan. From there, add a layer of the brown sugar and spice mixture and spread evenly.
Add the remaining bread batter on top of the brown sugar layer, then top with the remaining brown sugar and spice mixture.
Using a spoon, level the brown sugar and spice mixture while slightly swirling it into the top layer of the bread batter.
Bake for 55 minutes, or until a toothpick comes out clean.
Allow to completely cool before slicing and serving.