Whisk together first 5 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; sprinkle 1/2 cup pecans evenly on vanilla wafers. Pour half of pudding mixture on top of pecans in dish. Repeat layers with remaining vanilla wafers, pudding, and ending with pecans.
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° for 8 to 10 minutes or until golden brown.