Preheat oven to 350°F (175°C).
In a medium saucepan, whisk together 1/2 cup sugar, flour, and salt. Gradually stir in milk, and cook over medium heat until mixture is thickened and bubbly.
In a separate bowl, beat egg yolks slightly. Gradually whisk in about 1/2 cup of the hot milk mixture to temper the eggs. Return the egg mixture to the saucepan, whisking constantly. Cook for 2 more minutes, then remove from heat and stir in vanilla extract.
In a 2-quart baking dish, layer vanilla wafers, banana slices, and pudding mixture, starting with wafers and ending with pudding.
For the meringue, beat egg whites and cream of tartar on medium speed until soft peaks form. Gradually add 1/4 cup sugar, beating on high until stiff peaks form.
Spread meringue over the pudding, sealing to the edges of the dish.
Bake in the preheated oven for 12-15 minutes, or until the meringue is golden brown. Let cool before serving.