Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and set aside.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined; do not overmix.
Gently fold in the fresh blueberries until evenly distributed throughout the batter.
Pour the batter into the prepared cake pan and spread it out evenly.
Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.
Once cooled, dust the top of the cake with powdered sugar if desired.
Slice and serve the blueberry buttermilk breakfast cake. Enjoy!