Preheat oven to 400 degrees. Combine sugar & cornstarch (use 1/8 cup cornstarch for thinner pudding or 1/4 cup for thicker pudding) with a whisk or by sifting together. Whisk in milk. Add butter & microwave for 2 minutes. Whisk.
Beat egg yolks with whisk. Add 1/4 cup of hot milk mixture to egg yolks to temper, then add egg yolk mixture to milk mixture. Whisk well, and microwave for 2 minutes. Whisk, & repeat until mixture is thickened. Whisk in vanilla flavoring.
Layer 1/3 to 1/2 of the vanilla wafers in the bottom of a 3 quart bowl. Slice 3 bananas on top of the wafers. Repeat the layers.
Pour the thickened pudding mixture over the last layer of bananas.
For the meringue, beat the egg whites & cream of tartar on high until soft peaks form. Slowly beat in the sugar. Beat on high until stiff peaks form (mixture stays on beater when lifted out of bowl).
Spread the meringue on top of the pudding mixture. Bake for about 10 minutes, or until brown. Remove from oven & let cool. Refrigerate.