In a mixing bowl combine the flour, sugar, brown sugar, cinnamon and salt until well blended. Add melted butter and stir until evenly moistened.
Preheat the oven to 170 degrees C. Butter and flour a 23cm square baking tin.
In a bowl, combine flour, baking powder, bicarb soda and salt. In a separate bowl, toss the blueberries with 1 tablespoon of the flour mixture until coated. In another bowl, whisk together the sour cream and vanilla.
Using an electric mixer beat together the butter and white sugar until fluffy. Beat in the eggs one at a time. Beat in the flour in three additions, alternating with the sour cream mixture. Fold in the blueberries with a spatula. Pour the batter into the cake tin.
Sprinkle the crumble topping over the cake and bake until it tests done, about 45 minutes.