Preheat oven to 350 degrees. Generously coat a 9 x 5 metal loaf pan with nonstick cooking spray then set aside.
In a large mixing bowl, whisk together dry ingredients: flour, baking powder, salt and cinnamon.
In a separate bowl, beat butter, brown sugar and granulated sugar together for 2 minutes or until well combined. Scrape down the sides of the bowl as needed.
Add eggs, one at a time, and beat until smooth.
Add vanilla and beat until incorporated.
Reduce mixer speed to low then add dry ingredients to wet, mixing until just barely combined.
Add apples to batter, gently stirring by hand with a spoon until evenly distributed then pour into prepared loaf pan. Level top with a spatula. Note: batter will be thick.
Bake for 30 minutes then cover loaf with aluminum foil (to prevent overbrowning) and bake for an additional 30 to 35 minutes. Bread is done when a toothpick inserted into the center comes out clean and dry. For best results, avoid overbaking.
Cool loaf in pan for 10 minutes before turning out onto a wire rack to cool completely.