Preheat oven to 350°F (175°C) and grease a 9-inch cake pan.
In a mixing bowl, combine flour, baking powder, baking soda, and salt.
In another bowl, cream the butter and sugar until fluffy.
Add eggs one at a time, then mix in sour cream and vanilla.
Gradually blend dry ingredients into the wet mixture until smooth.
Gently fold in the blueberries.
Pour batter into the prepared pan.
For the topping, combine flour, brown sugar, and cinnamon.
Add cold butter, working it in until crumbly.
Sprinkle the crumb mixture evenly over the batter.
Bake for 35 minutes or until a toothpick comes out clean.
Let the cake cool before slicing.