Preheat oven to 350 degrees. Coat a round cake pan with cooking spray.
In a large bowl, cream together the sugar, butter. Add the egg and lemon zest then beat until fluffy.
In a separate bowl combine the flour, baking powder, and salt. Add the flour mixture to the creamed mixture, alternating with the milk. Mix until just combined.
Toss blueberries with 1 tablespoon flour. Fold into batter and spread the thick batter in the prepared pan.
Combine the streusel toppings together with your fingers until crumbly.
Sprinkle the streusel topping over batter evenly and bake 40-50 minutes or until a toothpick comes out clean.