Preheat waffle baker according to manufacturer's directions.
In a medium bowl whisk together the flour, baking soda, baking powder, salt, and sugar. In another bowl beat together the eggs and melted butter, and then add the buttermilk. Add the wet ingredients to the dry and stir until combined. Allow to rest for about 5 minutes.
Ladle the recommended amount of waffle batter onto the iron according to the manufacturer's recommendations (usually no more than 2/3 way full; if you pour too much, your waffle batter will ooze out!). Close the iron top and cook until the waffle is golden on both sides and can easily be removed from your waffle baker.