Preheat oven to 350 degrees F. Grease a 10 inch spring form pan well and line the bottom with parchment paper if you like for easy release of the cake when it is baked.

Cream together the butter and sugar until light and fluffy.

Add the eggs, one at a time. Beat well after the addition of each egg.

Beat in the vanilla extract.

Sift together the flour and baking powder.

Add dry ingredients alternately with the milk.

Always begin and end with an addition of dry ingredients. As a general rule, add the flour mixture in 3 divisions and the milk in two.

Be careful not to over mix the batter or your cake will be dense. Fold the batter only until the flour is incorporated but no more.

Quickly fold in the blueberries.

Spread batter evenly into the prepared pan.

Mix together the flour, sugar and cinnamon.

Using your finger tips rub the butter through the dry mixture until it resembles a coarse meal.

Press the crumb mixture together in handfuls and break off small pieces about the size of the top of your pinky finger, scattering them over the surface of the batter.

Bake at 350 degrees F for about 35-40 minutes or until a toothpick inserted in center comes out clean. The baking time can vary, especially if you use frozen berries. In that case it may take 10 or even 15 minutes more to bake. The toothpick test is the best way to ensure that this cake is fully baked.