In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, and salt. Make sure everything is evenly distributed so your waffles rise consistently. This only takes about a minute of whisking.
In a separate bowl, whisk the warm buttermilk with the melted butter until smooth. Add in the eggs and stir until fully combined. Warming the buttermilk slightly helps the butter stay melted and blend more evenly.
Pour the dry mixture into the wet ingredients and whisk just until combined. A few small lumps are completely fine and actually help keep the texture tender. Overmixing at this stage is the number one reason waffles turn out tough.
Fold in the vanilla extract, then let the batter sit for about 10 minutes. This resting period allows the flour to hydrate fully and helps the waffles brown more evenly. Don't skip this step even if you're in a rush.
While the batter rests, preheat your waffle iron and lightly grease the plates. A properly heated iron is key to getting crisp, golden edges. Cold or under-heated irons tend to produce pale, soft waffles.
Pour about ⅓ to ½ cup of batter onto the hot iron, spreading it just to the edges. Close the lid and cook until the steam slows and the waffle turns deep golden brown. Repeat with the remaining batter, keeping cooked waffles warm as you go.