Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
In a separate bowl, cream together the softened butter, eggs, and vanilla extract.
Gradually add the wet ingredients to the dry ingredients, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined.
Gently fold in the blueberries.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.
Notes
Enjoy this cake on its own or with a dusting of powdered sugar.