Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon. Set aside.
In a large bowl, cream butter and sugar together until light and fluffy. Beat in eggs one at a time, then stir in the vanilla.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the apples.
Pour the batter into the prepared pan and smooth the top. Bake in preheated oven for 40 minutes or until a toothpick inserted into the center comes out clean.
Notes
Let the cake cool in the pan for about 10 minutes before turning it out onto a wire rack. Serve warm or at room temperature, dusted with powdered sugar if desired.