Place shredded potatoes and onion in medium size fry pan prepared with vegetable spray (if you don't have shredded potatoes on hand refer to note below). Keep potatoes separated as much as possible while browning, you do not want a patty.
When potatoes are well browned add ham cubes and mix well.
Lower heat to medium low. Pour egg substitute evenly over potato mixture and cook till almost set. Turn mixture over (it will not turn easily or neatly but after turning simply spread with spatula to an even round shape).
When eggs are set well tear cheese slice into strips and lay across one half of the omelet. Fold omelet in half over the cheese slice and serve.
NOTE: No cooked potatoes on hand? Microwave a potato for about 2-3 minutes. Slice in half lengthwise and place in cold water for about 2-3 minutes. Shred each half without peeling. Keep the peel against your palm while shredding and most of the peel will remain in your hand. Discard the peel and continue with recipe.