Preheat the oven to 400 degrees. Mix together the softened butter and coconut flour in a medium sized bowl until a crumbly mixture forms. Add the eggs and mix until you have a dough.
Press into a greased 9-inch pie pan and bake for 10 minutes.
Add cold water to a bowl and sprinkle gelatin over top. Let soften for a minute, then stir in hot water until gelatin dissolves.
Add the heavy cream to a saucepan and heat until it is hot but not boiling. Meanwhile, whisk the egg yolks in a small bowl.
Pour about half a cup of the hot cream into the egg yolks and whisk, then pour the egg mixture into the saucepan while whisking.
Reduce the heat to low and stir in the sweetener, banana extract and gelatin. Remove from heat and let cool slightly.
Pour the filling into the cooled pie crust and refrigerate for 2 hours or until firm.
To make the topping, beat the cream and powdered sweetener with a mixer on medium speed until thick. Spread the whipped cream over the filling and refrigerate another 1-2 hours.