In a medium saucepan, combine granulated sugar, all-purpose flour, and a pinch of salt. Gradually whisk in whole milk and the egg yolks, mixing until smooth. Place over medium-low heat, stirring continuously for about 10-12 minutes, or until thickened. Stir in vanilla extract and remove from heat.

In a trifle dish, spread a layer of custard, then arrange a layer of Nilla wafers followed by sliced bananas. Repeat layers until all ingredients are used, finishing with custard.

Preheat oven to 400°F. In a clean bowl, beat egg whites until soft peaks form. Gradually add granulated sugar while beating until stiff peaks form. Spread meringue over the pudding, sealing the edges.

Bake for about 5 minutes until meringue starts to set. Switch to broil for 1-2 minutes until golden brown.

Let the pudding cool at room temperature for 30 minutes, then cover and refrigerate for at least 2 hours.