• 1 cup water
• 2 lbs. potatoes (about 6 medium)
• 1/2 teaspoon cream of tartar
• 1/4 teaspoon pepper
• 1 small onion, thinly sliced
• 1/4 cup flour
• pepper
• 3 tablespoons butter
• 1 (10.5 oz.) can cream of mushroom soup
• 4 slices American cheese
• 1 teaspoon salt

Peel and thinly slice potatoes.  Toss with 1 cup water and cream of tartar.  Drain.  Put half of the sliced potatoes in a greased slow cooker.  Top with half the onions, flour, salt and pepper.  Add butter and undiluted soup.  Cover and cook on low for 7 to 9 hours (or on high for 3 to 4 hours).  Add cheese slices on top 30 minutes before serving.