Preheat oven to 350 degrees. Spray a 9x13 pan with cooking spray. In a large bowl, add all ingredients except lemon zest, blueberries and flour.
Mix on low until moistened, then on high for 2 minutes. In a separate bowl, toss the blueberries and flour until the berries are well coated,
Gently fold in 1 cup of the blueberries and the lemon zest to the mixture. Pour into prepared 9x13 pan.
Drop the remaing cup of blueberries on top and gently press into batter. Discard extra flour remaing in bowl from berries.
Cook at 350 degrees for 40-50 minutes or until lightly browned and a toothpick inserted comes out clean.
After removing from oven, sprinkle top with sugar. (Optional)