1. In a small oven proof bowl, combine diced onion, pepper and kielbasa. Precook in toaster oven for about 5 minutes (or microwave for a minute), to soften slightly.
2. Heat ghee in a large skillet over medium-high. In a bowl, whisk together eggs and water. Season with salt and pepper.
3. Slightly reduce heat and pour the egg mixture into the skillet. Tilt the skillet so eggs fully cover the entire bottom. When edges start to set, use a wide spatula to slightly push cooked edges toward the center, then tilt the skillet to allow uncooked portion fall to the edges.
4. When no visible liquid egg remains, add precooked sausage, peppers and onions to one side of the omelette. Top with cheese.
5. Using the same spatula (it's easier when you use a wide and thin-edged one), fold other side over cheese.
Reduce heat to low, cover the skillet, let stand for another minute. Slide onto a plate and serve.