Sift flour, baking powder and baking soda into a medium-sized bowl then add sugar and salt. Stir to combine. In a small bowl, beat egg well then stir in buttermilk and vanilla until completely combined.
Make a well in the center of flour mixture then pour in buttermilk mixture and melted butter. Gently stir to bring the wet and dry ingredients together only until no dry spots remain and the mixture is uniform in consistency. It will have small lumps of flour, which is normal. Set batter aside to rest while you prepare the skillet.
If you have an electric skillet or griddle, now is the time to heat it to 350 degrees. Otherwise, place a large non-stick skillet over medium heat then let it come to temperature. Spray skillet with a light coating of cooking spray then add about ⅓–½ cup of batter for each 5"–6" pancake. Handle batter gently and do not stir, as you are trying to preserve as many bubbles in the batter as possible.
Spread batter gently, letting the pancakes cook for 2–3 minutes on the first side or until nicely browned. The batter will continue to spread as it cooks. Flip pancake over then cook an additional 1–2 minutes or until the center is firm to the touch and springs back when pressed.
Remove from skillet and repeat with remaining batter. Serve nice and hot with plenty of butter and maple syrup.
One Last Thing
You can totally make the batter a day in advance. Just take care to cover it with plastic wrap then store it in the fridge overnight.