Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, and salt.
In another bowl, cream the softened butter until light and fluffy.
Add the eggs one at a time to the butter, beating well after each addition.
Stir in the vanilla extract.
Gradually combine the dry ingredients with the wet mixture until just combined.
Gently fold in the diced apples until evenly distributed.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes before transferring to a wire rack to cool completely.