In a medium sized bowl, mash the banana with a fork. Then stir in the vanilla extract and egg.
Once the butter has cooled down, pour it into the mixture and stir until combined.
Next, pour in the cassava flour, baking soda, and pinch of salt. Stir it a little and then pour in the water and continue mixing until the batter is smooth. The batter will be thick, but add an extra tablespoon of water if needed.
Heat a non-stick pan or griddle to medium-high temperature. Scoop out about 4'' pancake rounds and cook for 4 minutes. Use a spatula to flip the pancake over and cook for another 4 minutes. Serve warm.