Mix together butter and sugar until light and fluffy.
Add in eggs, one at a time. Scrape down bowl.
Add in sour cream, lemon juice and vanilla.
Add in flour (minus a tablespoon), baking powder, baking soda and salt.
Mix to combine, do not over beat.
Sprinkle blueberries with remaining 1 tablespoon flour and stir to coat the berries.
Gently fold berries into the batter.
Pour batter into prepared pan and spread evenly.
Cover the top with the streusel mixture.
Bake for 40-50 minutes in the tube pan, 30-35 minutes in a 9x13 or cake pan.
Insert a toothpick to see if cake is done, should come out clean.
Remove from oven and allow to cook on a rack.
Remove from pan after it has cooled.