Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan.
In a large bowl, whisk together the flour, ¾ cup of the granulated sugar, baking powder, salt, and 1 teaspoon of the cinnamon.
In a separate bowl, whisk together the milk, eggs, melted butter, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix – a few lumps are okay.
In a small bowl, toss the diced apples with the remaining ¼ cup of granulated sugar.
In another small bowl, combine the brown sugar and the remaining 1 teaspoon of cinnamon.
Pour about one-third of the batter into the prepared loaf pan. Sprinkle half of the cinnamon-sugar mixture evenly over the batter. Top with half of the sugared apples.
Add another one-third of the batter, then the remaining cinnamon-sugar mixture, and the remaining apples. Finish with the final one-third of the batter.
If you want a pretty swirl throughout the bread, you can use a knife or a skewer to gently swirl the layers together.
Bake for 50-60 minutes, or until a wooden skewer inserted into the center comes out clean or with just a few moist crumbs attached.
Let the bread cool in the pan for about 10-15 minutes before transferring it to a wire rack to cool completely.