In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In a separate bowl, combine the buttermilk and melted butter. Beat in the eggs until smooth.
Gently fold the dry ingredients into the wet until just combined, leaving a few lumps. Stir in the vanilla extract. Allow to rest for 10 minutes.
Heat the waffle iron and lightly grease it with cooking spray.