Preheat your oven to 350°F (175°C).

Peel, core, and slice about 4 cups of tart apples into bite-sized pieces and toss with cinnamon.

Cream together softened butter and granulated sugar for 3-4 minutes until light and fluffy.

In a separate bowl, whisk together flour, baking powder, cinnamon, and a pinch of salt, then combine with the butter-sugar mixture.

Add eggs one at a time and vanilla extract, mixing until fully combined.

Fold in the cinnamon-coated apple slices gently.

Pour the batter into a greased 9-inch round cake pan and bake for 40-45 minutes until golden brown.

Allow the cake to cool in the pan for 10-15 minutes before transferring to a wire rack to cool slightly.