Preheat oven to 350 degrees. Butter and flour a 9 - inch round baking pan.
For the Streusel topping:
Melt the butter. Combine granulated sugar, brown sugar, pecans and cinnamon in a medium bowl. Stir in the flour and melted butter. Mix and set aside.
For the cake:
In a medium bowl, combine the flour, baking soda, baking powder and salt. Whisk and set aside.
In the bowl of a standing mixer fitted with a paddle attachment, combine softened butter and sugar. Mix on medium high speed until light and creamy, about 4 minutes. Reduce speed to low and add the eggs one at a time, mixing well after each addition. Stir in vanilla, lemon zest and sour cream. Scrape down the sides of the mixing bowl and paddle attachment.
Stir in the dry ingredients until just combined. Fold in the blueberries and stir until the batter is just combined.
Spoon the batter into the prepared pan. Crumble the topping evenly over the batter and bake for 40 - 50 minutes. Test with a toothpick to confirm it's done.