Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan.

In a large bowl, cream the softened butter, granulated sugar, and brown sugar together until the mixture is light and fluffy.

Beat the eggs into the mixture one at a time, ensuring that they are fully incorporated before adding the next. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually mix this dry combination into the creamed mixture, alternating it with the buttermilk, ensuring a well-blended batter after each addition.

Gently fold in the butterscotch chips and chopped nuts, if desired, to add texture and flavor.

Pour the batter into the prepared cake pan and smooth the top with a spatula.

Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean.

Once baked, remove the cake from the oven and allow it to cool before spreading with the butterscotch frosting.

For an extra layer of crunch, top with additional chopped nuts or a sprinkle of crushed cookies before serving.