Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan.
Spread the blueberries evenly on the bottom of the prepared cake pan. Sprinkle the brown sugar over the blueberries.
In a medium bowl, whisk together the flour and baking powder.
In a separate large bowl, cream together the butter and granulated sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, alternating with the milk, starting and ending with the dry ingredients. Mix until just combined.
Pour the batter over the blueberries in the cake pan. Spread evenly.
Bake in the preheated oven for 45 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Allow the cake to cool in the pan for about 10 minutes, then invert onto a serving plate.