In a large bowl, combine the flour, baking soda, baking powder, salt, and sugar.
In a separate bowl, whisk the eggs. Then add the melted butter, vanilla, and buttermilk. The buttermilk at room temperature prevents the melted butter from firming up when mixing.
Add the wet ingredients into the dry ingredients bowl, and stir to combine. Let the batter sit for 5 minutes. Meanwhile, preheat the waffle iron.
Cook the waffles:
Heat the waffle maker to your preferred setting. If your waffle maker has an adjustable temperature gauge, I recommend setting it to medium-high. Grease it if necessary (some non-stick waffle makers don't need it; you know yours best).
Scoop some of the batter into the center of the hot waffle maker and spread it out with the back of the spoon towards the edges without overfilling. The batter expands, so you want to see some of the tops (squares). Close the lid and cook until steam stops coming out the sides and they're golden brown. Repeat with the remaining batter. Keep them warm on a sheet pan in a 200F oven.
Serve & Store:
Serve these waffles with your favorite toppings and syrups. Refrigerate leftovers for up to 3 days or freeze for up to 3 months.