Combine 1/2 cup sugar, flour, and salt in the top of a double boiler.

Stir in milk until well combined.

Cook over boiling water, stirring constantly, until the mixture thickens.

Continue cooking, uncovered, for 15 minutes more, stirring occasionally.

Beat egg yolks in a separate bowl.

Gradually stir a small amount of the hot mixture into the egg yolks to temper them.

Pour the egg yolk mixture back into the double boiler.

Cook for 5 minutes, stirring constantly.

Remove from heat and stir in vanilla extract.

Line the bottom of a 1 1/2-quart casserole dish with vanilla wafers.

Top with a layer of sliced bananas.

Pour a portion of the custard over the bananas.

Continue to layer vanilla wafers, bananas, and custard, ending with custard.

In a clean bowl, combine the remaining 1/4 cup sugar and egg whites.

Beat until stiff peaks form.

Pile the meringue on top of the pudding in the casserole dish.

Bake in a preheated hot oven until the meringue is lightly browned.