Preheat oven to 350 degrees. Spray a 9" spring form pan with non-stick baking spray, and set aside.

In a bowl, add flour, baking powder and salt. Whisk together and set aside.

In large mixing bowl, cream the butter and sugars together until completely combined. Add the eggs one at a time while mixer is on low. Mix in vanilla and sour cream. With mixer still on low, gradually add the the dry ingredients and mix until batter is smooth. Lastly, add the lemon juice and beat on low until combined into the batter.

In a separate bowl, add the blueberries and lemon zest. Stir in the last tablespoon of flour and thoroughly coat the blueberries and zest. Fold the fruit mixture into the batter. Pour the batter into the prepared pan.

In another bowl, combined the slightly melted butter, flour and brown sugar. Mixture will be crumbly. Evenly sprinkle/crumble the streusel over the top of the batter.

Bake at 350 for 1 hour, 20 minutes, to 1 hour 30 minutes. Ensure the cake is set and cooked through by lightly moving the pan. If the batter giggles, its not done. Batter needs to be set in the center, golden brown, and when inserting a toothpick, it should come out clean of crumbs.

Take out of the oven, let cool for about 15 minutes before removing from the pan. To make the glaze, combine the lemon juice and powdered sugar. Stir until fully combined and drizzle over the cake.