Preheat your oven to 350°F (175°C) and grease a standard 9x5-inch loaf pan, lining it with parchment paper for easy removal.
Peel and dice the apples into small bite-sized cubes, then toss them lightly with a pinch of flour to prevent sinking.
In a medium mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, and salt.
In a separate large bowl, whisk together the melted butter, granulated sugar, brown sugar, eggs, milk, and vanilla extract until smooth.
Gently fold the dry ingredients into the wet mixture using a spatula just until combined, taking care not to overmix the batter.
Fold in the prepared diced apples until evenly distributed throughout the thick batter.
Transfer the batter into your prepared loaf pan, smoothing out the top, and sprinkle the extra cinnamon-brown sugar mixture evenly over the surface.
Bake for 50 to 60 minutes until a toothpick inserted into the center comes out clean, then let cool completely before slicing.