Preheat your oven to 350°F (175°C) and grease and flour a cake pan.

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

In a large mixing bowl, cream the sugar and softened butter together until light and fluffy, about 2-3 minutes.

Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract.

Gradually add the dry mixture to the wet ingredients, mixing until just combined. Avoid overmixing.

Gently fold in the chopped apples and walnuts until evenly distributed.

Pour the batter into the prepared cake pan and smooth the top.

Bake for 45-50 minutes or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.