Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round or square cake pan.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, and ground cinnamon.
In a large mixing bowl, cream together softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time, followed by the vanilla extract.
Stir in sour cream (or yogurt) until well combined.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the diced apples gently.
Pour the batter into the prepared cake pan and spread evenly.
Bake for 35-40 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool completely before dusting with powdered sugar or drizzling with glaze, if desired.
Slice and serve!