Preheat your oven to 350°F (175°C).
Grease and flour a Bundt pan.
In a mixing bowl, cream the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Mix in the buttermilk and vanilla extract.
In another bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt.
Gradually add the dry ingredients to the wet mixture.
Fold in the diced apples and nuts (if using).
Pour the batter into the prepared Bundt pan.
Bake for 55-65 minutes or until a toothpick comes out clean.
Allow the cake to cool in the pan for 15 minutes before inverting onto a wire rack.
Dust with powdered sugar or glaze with icing before serving.
