Whisk together first 4 ingredients in a large saucepan over medium-low heat; cook, whisking constantly, 6 to 8 minutes or until thickened. Remove from heat, and stir in vanilla. Let stand 5 minutes. Gently stir bananas into pudding mixture.

Arrange 15 vanilla wafers in a single layer on bottom of a 1-1/2-quart baking dish; pour half of pudding mixture over wafers in dish. Repeat layers with remaining vanilla wafers and pudding.

Beat egg whites and 1/8 teaspoon cream of tartar at high speed with an electric mixer until foamy. Add 2 tablespoons sugar, 1 tablespoon at a time, beating until soft peaks form and sugar dissolves (about 1 to 2 minutes). Spread meringue evenly over top of banana mixture, sealing edges. Bake at 400 degrees for 8 to 10 minutes, or until golden brown.