Preheat the oven to 350°F (175°C). Grease the 9-inch round cake pan and line the bottom with parchment paper for easy removal.

In a medium bowl, sift together the flour, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, cream the butter and granulated sugar together using an electric mixer until light and fluffy, about 3-5 minutes.

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

Alternately add the dry flour mixture and the buttermilk to the creamed mixture, starting and ending with the flour mixture. Mix until just combined.

Gently fold in the cranberries, making sure they are evenly distributed throughout the batter.

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

Bake in the preheated oven for 45-50 minutes, or until a toothpick inserted in the center comes out clean.

Remove the cake from the oven and place it on a cooling rack for about 10 minutes. Then, carefully turn it out of the pan and let it cool completely on the rack.

If desired, mix the powdered sugar with the water to create a simple icing. Drizzle over the cooled cake before serving.

For a festive touch, you can garnish the cake with additional fresh cranberries or a sprinkle of powdered sugar before serving.