Preheat oven @ 350 degrees. Coat a 13 x 9 baking dish with cooking spray. Place 1/2 of the raw potatoes on the bottom, 1/2 the onions, crumble 1/2 the raw ground beef over that, followed by 1/2 the beans. Repeat the layer. Mix the water with the tomato soup and pour over the ingredients. Sprinkle with salt and pepper. Place dabs of butter over the top and bake covered for approximately 1 hour, then bake uncovered for 30 minutes or until the potatoes are cooked.