Preheat your oven to 350°F (175°C) and grease and flour the 9-inch round cake pan.
In a medium bowl, combine the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Whisk together until well blended.
In a large mixing bowl, cream together the softened butter and granulated sugar using an electric mixer or whisk until light and fluffy (about 3-5 minutes).
Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
Gradually add the dry ingredient mixture to the wet ingredients, alternating with the buttermilk. Begin and end with the dry ingredients, mixing until just combined.
Gently fold in the cranberries and nuts (if using) until evenly distributed throughout the batter.
Pour the batter into the prepared cake pan and spread it evenly.
Bake in the preheated oven for 45 minutes or until a toothpick inserted in the center comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes before transferring it to a cooling rack to cool completely.
Once cooled, dust the top of the cake with powdered sugar for decoration.