In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In another bowl, whisk together the buttermilk, eggs, melted butter, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
Lightly grease the waffle iron with cooking spray or melted butter. Pour the batter onto the waffle iron and cook according to the manufacturer's instructions until golden brown and crisp.