Preheat the oven to 175 degrees C. In a large bowl, mix ricotta, spinach, onion and egg. Mix the mixture with parsley, pepper and garlic powder. Mix in 1 cup mozzarella and 1/4 cup parmesan.
In a separate bowl, mix the spaghetti sauce and water.
Pour a cup of diluted sauce into the baking dish. Lay out large pasta stuffed with spinach, fill with the rest of the sauce. Sprinkle with the remaining cheese.
Bake in a preheated oven for 45 minutes.