Preheat the oven to 350°F.

Set a large skillet over medium-high heat and add the olive oil. When the oil is hot, add onion and cook for 3 minutes, stirring frequently, until softened. Add the garlic and continue cooking for an additional 30 seconds. Remove from heat and set aside to cool.

In a medium bowl, combine the ricotta cheese, 1 tablespoon parsley, Italian seasoning, black pepper, and garlic powder. Stir in 1 cup of the mozzarella and 1/4 cup of the Parmesan cheese.

Use a small spoon or pastry bag to stuff the ricotta mixture into the uncooked manicotti tubes and set aside.

In a large bowl, whisk together the spaghetti sauce and water. (Tip: Add the pasta sauce to the bowl, then pour 1 cup of water into the jar and swirl it around to get all the sauce, then pour into the bowl.) Spread 1/2 cup of the sauce/water mixture over the bottom of a 9x13-inch baking dish.

Arrange the stuffed manicotti in a single layer. Cover with the remaining sauce. It will be very watery; this is normal. Sprinkle with the remaining 1/2 cup mozzarella and 1/4 cup Parmesan cheese,

Cover with aluminum foil and bake for 55 minutes, until the pasta tubes are cooked to al dente consistency; test this with a fork.

Remove foil and continue baking for 10 minutes. Remove from the oven and let the manicotti stand for 15 minutes to absorb any excess liquid from the sauce. The dish will firm up as it stands.

Sprinkle with the remaining 1 tablespoon of parsley and serve hot.