Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan.

In a large mixing bowl, cream together softened unsalted butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then fold in the sour cream until smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, salt, and ground cinnamon; then gradually mix it into the wet ingredients.

Fold in the chopped apples carefully, ensuring they're evenly distributed without overmixing.

Pour half the batter into the prepared loaf pan, layer with half the apples and sprinkle half of the sugar-cinnamon mixture on top.

Repeat with the remaining batter, apples, and sugar-cinnamon mixture.

Bake for 50-60 minutes, checking with a toothpick for doneness; it should come out clean.

Allow to cool in the pan for 10-15 minutes before transferring to a wire rack to cool completely.