Combine flour, sugar, baking powder, and baking soda in a large bowl.
Combine buttermilk, eggs, and oil in another bowl. Whisk liquid mixture into flour mixture until just combined. Do not overmix, batter should be lumpy.
Set the batter aside to rest for 10 minutes.
Spray a 10-inch cast iron skillet or similar sized oven-safe nonstick pan with cooking spray.
Pour batter into pan. Spread evenly and top with 1 ½ cups blueberries.
Place in oven. Bake for 10-12 minutes, or until toothpick inserted comes out clean.
Cut into 12 wedges and serve with remaining blueberries. Drizzle with syrup, if using.
Notes
Change it Up
Use ¾ cup of all-purpose flour and ¾ cup whole-wheat flour.
Try other berries. Add raspberries to one half and sliced strawberries to the other.
For extra flavor, add 1 teaspoon lemon zest or ½ teaspoon lemon juice to the batter.