Preheat oven to 350F. Mix gluten free graham cracker crumbs, melted butter, and sugar together. Press firmly into the bottom and up the sides of a 9-inch pie dish. Bake for 10 minutes until set. Let cool completely.
In a medium saucepan, whisk together sugar, cornstarch, and salt. Gradually whisk in milk and egg yolks. Cook over medium heat, whisking constantly, until the mixture thickens and begins to bubble, about 6 to 8 minutes.
Remove from heat and stir in butter and vanilla extract until smooth. Press plastic wrap directly onto the surface of the pudding and let cool for 15 minutes.
Arrange a layer of sliced bananas on the bottom of the cooled crust. Pour half the warm pudding over the bananas. Add another layer of banana slices, then pour the remaining pudding on top. Press plastic wrap onto the surface and refrigerate for at least 4 hours until fully set.
Before serving, whip heavy cream, powdered sugar, and vanilla extract together until stiff peaks form. Spread or pipe over the chilled pie. Garnish with a few extra banana slices and serve cold.