Preheat waffle maker. Spray generously with nonstick cooking spray or generously grease with butter.
In a large bowl whisk together flour, baking powder, baking soda, and salt.
In a separate large bowl, whisk together the buttermilk, sourdough discard, eggs, melted butter, vanilla, and sugar until blended. Add dry ingredients to wet ingredients and mix until just combined.
Allow ingredients to rest for at least ten minutes.
Pour batter into a preheated prepared waffle iron; cook according to manufacturer's directions or when steam stops.
Makes 4 waffles.