Heat oven to 350°F.

Mix  1/2 cup sugar, flour, and salt in top of a double boiler. Blend in 3 egg yolks and milk. Cook, uncovered, over boiling water 10 to 12 minutes or until thickened, stirring constantly. Remove from heat; stir in vanilla.

Reserve 12 wafers for garnish. Spread small amount of custard onto bottom of 1-1/2-quart baking dish. Cover with layers of 1/3 each of the remaining wafers, bananas and remaining custard. Repeat layers 2 times for a total of three layers (plus the thin layer of custard on the bottom.)

Beat the egg whites on high speed of mixer until soft peaks form. Mix cream of tarter with the remaining sugar and gradually beat in remaining sugar until stiff peaks form. Spread over custard, sealing well to edge of dish.

Bake  15 to 20 minutes or until lightly browned. Cool slightly. Top with reserved wafers just before serving.