Method:
Preheat oven to 350°F. Grease a 7- x 11-inch baking pan with oil and set it aside.
In a large mixing bowl, whisk together cornmeal, 2 cups of the flour, baking powder, baking soda, salt and sugar. Stir in lemon juice, zest, oil, egg and egg whites, buttermilk and vanilla, stirring after each addition until combined and smooth. Toss blueberries with remaining 1 tablespoon flour in a large bowl then gently fold into batter.
Pour batter into prepared pan and bake for 45 minutes, or until a toothpick inserted into the center comes out clean. Set aside to let cake cool until just warm then cut into squares and serve.