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

In a medium bowl, whisk together flour, baking powder, baking soda, salt, and 1 teaspoon of ground cinnamon.

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

Beat in the egg and vanilla extract until well incorporated.

Stir in the sour cream until the mixture is smooth.

Gradually fold the dry ingredients into the wet ingredients until just combined, being careful not to overmix.

Toss the diced apples with the remaining 0.5 teaspoon of cinnamon and fold them gently into the batter.

Transfer the batter into the prepared loaf pan and smooth the top with a spatula.

Bake for 55 to 65 minutes, or until a toothpick inserted into the center of the loaf comes out clean.

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