Preheat your oven to 350°F (175°C) and grease and flour a 9×13 inch cake pan (or two 9-inch round pans).

In a bowl, combine the flour, baking powder, baking soda, and salt. Stir and set aside.

In a large mixing bowl, beat the softened butter and granulated sugar together until light and fluffy, about 3-5 minutes.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually add the dry mixture into the butter mixture, alternating it with the buttermilk. Mix until just combined—do not over-mix.

If using, gently fold in the nuts or chocolate chips into the batter.

Pour the batter into the prepared cake pan and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

Let the cake cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.