Preheat a cast iron or non-stick skillet over medium heat. Lightly grease with butter.
Add sugar, salt, egg, melted butter, and vanilla to the fermented batter. Mix gently.
Sprinkle baking soda evenly over the batter and stir just until combined. The batter will become light and airy.
Pour ¼ cup batter per pancake onto the skillet. Cook until bubbles form and edges look set, about 2–3 minutes.
Flip and cook another 1–2 minutes until golden brown.
Serve immediately or keep warm in a low oven.