Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.

In a bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

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

Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.

Gradually add the dry ingredients to the wet mixture, alternating with milk, and mix just until combined.

Fold in the diced apples and cinnamon gently into the batter.

Divide the batter evenly among the cupcake liners, filling each about 2/3 full.

Bake for 18-20 minutes, or until a toothpick inserted in the center comes out clean.

Let the cupcakes cool in the pan for a few minutes before transferring them to a wire rack to cool completely.

For optional frosting, mix powdered sugar with milk until smooth and drizzle over cooled cupcakes.