In a large bowl, whisk together the flour, sugar, baking powder, baking soda and salt; set aside.
In a medium bowl, whisk together the buttermilk, butter, eggs and vanilla extract. Add the wet ingredients to the dry ingredients and gently whisk to combine. Do not overmix!
Spray a waffle iron with non-stick cooking spray, then preheat. Once the waffle maker is ready, add the batter according to the manufacturer's instructions and cook for 2 to 3 minutes, or until the waffle maker indicates they are ready. Serve immediately, or place in a 300-degree oven to keep warm. Leftover waffles can be wrapped in plastic wrap, placed in a ziploc bag and stored in the refrigerator for 2 days or in the freezer for up to 1 month.