In a saucepan, combine sugar, custard powder and salt in a saucepan and add the milk, whisking to combine. Bring these ingredients to the boil, stirring all the time, until thickened. Add vanilla and set aside. Arrange half the vanilla wafers on the base of an ovenproof casserole dish and top with sliced banana. Spoon half of the custard over and repeat the layers with remaining wafers, banana and custard. Beat egg whites and cream of tartar together until soft peaks form. Add the sugar, 1 teaspoon at a time, beating well after each addition, until the meringue is thick and glossy. Spread over custard, sealing edges of dish well so that no custard is visible and bake at 170c. for 30 minutes or until golden brown. Per serving: 374 Calories (kcal); 2g Total Fat; (3% calories from fat); 11g Protein; 85g Carbohydrate; 0mg Cholesterol; 247mg Sodium Food Exchanges: 0 Grain(Starch); 1 Lean Meat; 0 Vegetable; 5 1/2 Fruit; 0 Fat; 0 Other Carbohydrates Converted by MM_Buster v2.0n.