Preheat your oven to 350°F (175°C). Grease and flour an 8 x 5 inch loaf pan or line it with parchment paper. Set it aside.

In a small bowl, mix together the brown sugar and cinnamon. Set this mixture aside for later.

In a large mixing bowl, whisk the eggs and granulated sugar together until they are well combined.

Stir in the melted butter and vanilla extract until the mixture is smooth.

Add in the all-purpose flour, baking powder, baking soda, and salt. Mix until everything is just combined. The batter will be quite thick.

Gently fold in the chopped apples.

Pour half of the batter into the prepared loaf pan. Sprinkle about three-quarters of the brown sugar mixture over this layer of batter.

Spread the remaining batter on top of the brown sugar mixture. Then sprinkle the rest of the cinnamon sugar over the top and gently swirl it into the batter using a knife or spoon.

Bake for 35 to 45 minutes, or until the top is golden and a toothpick inserted into the bread comes out clean (or with just a few moist crumbs). If the bread is browning too quickly, cover it loosely with foil for the last 10 to 15 minutes of baking.

Let the bread cool completely before slicing and serving.