Heat oven to 375°F. Spray 9-inch square pan with cooking spray.
In large bowl, mix 1 cup flour, the granulated sugar, baking powder, cinnamon and 1/4 teaspoon salt. Add 1/2 cup melted butter, the milk, egg and vanilla; mix well. Mash 1 banana (about 1/2 cup), and add to batter; mix well. Pour into pan. Cut remaining banana into 1/4-inch slices; place in single layer over batter.
In medium bowl, mix 1/2 cup flour, the brown sugar, oats and 1/8 teaspoon salt. Stir in 1/2 cup melted butter. Add cereal and pecans; mix well. Sprinkle topping over banana slices.
Bake 30 minutes. Remove from oven, loosely cover with foil. Bake 10 to 15 minutes longer or until toothpick inserted in center comes out clean. Place on cooling rack; cool 15 minutes before serving. Serve with vanilla ice cream, if desired.