In a large mixing bowl, stir together the flour, sugar, baking powder, and salt. Make a "well" in the center of the dry ingredients; set aside. In a smaller mixing bowl, combine the eggs, milk, melted butter, and vanilla. Pour the egg mixture into the flour mixture and stir just until moistened, being careful not to over-mix.

Heat the waffle iron according to manufacturer's directions. Spray with cooking spray. Ladle approximately 3/4 cup batter (or however much your waffle iron will hold) into the waffle iron. Cook for 2 to 3 minutes, or until lightly browned. Lift open the waffle iron, add several pieces of pineapple and banana slices, sprinkle with brown sugar, and then continue cooking another 2 to 3 minutes, or until the waffle iron timer goes off. Repeat until the batter is finished. Serve immediately. Serves 6.