In a medium-sized bowl, mix butter and sugar until creamy.

Add eggs and vanilla and beat until smooth.

In a large bowl, combine flour, pudding mix, salt and baking powder by stirring with a fork until blended.

Make 2 wells in the flour mixture and pour the milk into one and the egg mixture in the other.

Using a large spoon, gradually fold in the ingredients until a thick batter is formed.

Now put about 2 Tablespoons flour into a shallow dish and pour in the blueberries with the flour thoroughly coating the blueberries with the flour (this keeps them from  sinking to the bottom).

Then pour all of the blueberries and flour into the batter and fold in gently.

Spray a bread pan with cooking spray and pour the batter into the pan.  (Some people like to use parchment paper to aid in releasing the cake.)

Bake at 350 degrees for 65 minutes.  The cake is done when a toothpick inserted in the middle of the cake comes out clean.

Take it from the oven and let it sit a couple of minutes before releasing the cake.

To release the cake, run a knife or spatula around the sides of the warm cake and turn over onto a cooling rack.  A cool cake will not release well and may break apart.