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.