2tablespoonscoarse sugar(such as Sugar in the Raw or Demerara)
Preheat thee oven to 350 degrees F. Spray a 9-inch springform pan with nonstick spray. Do not use a 9-inch cake pan- it won't be big enough.
In a large bowl, whisk together the flour, baking powder, baking soda and salt; make a well in the center.
In a medium bowl, whisk together the buttermilk, sugar, oil, eggs, egg whites and lemon zest. Pour into the well of the flour and stir to combine (a few lumps in the batter are OK- do not over mix).
In a medium bowl, toss the blueberries with the 1 tablespoon of flour to evenly coat. Fold all but 1/2 cup of the blueberries into the batter. Spread the batter into the prepared pan and top with the remaining 1/2 cup blueberries.
Sprinkle with the coarse sugar and bake until the cake is brown and a wooden pick inserted into the center comes out clean, 70 to 75 minutes.
Let the cake cool in the pan for 15 minutes, then remove the outer ring and transfer to a wire rack to cool completely.