Add the onion, garlic, egg, bread crumbs, ketchup, parsley, Parmesan, Pecorino, salt and pepper to a large bowl and blend. Mix in the turkey. Shape the turkey mixture into 1 1/4-inch-diameter meatballs. Place on a large plate or baking sheet.
Heat the oil in a heavy large frying pan over medium-high heat. Add the meatballs and saute until browned on all sides, about 5 minutes. Turn off heat.
Transfer the meatballs to a plate. Pour off any excess oil. Add the marinara sauce, about 3 cups. Return all the meatballs to the pan. Turn the heat to medium-low and simmer until the sauce thickens slightly and the flavors blend, 15 to 20 minutes. Season the sauce, to taste, with salt and pepper. Transfer the meatball mixture to a serving bowl. Serve with toothpicks.
Simple Tomato Sauce:
In a large casserole pot, heat oil over medium high heat. Add onion and garlic and saute until soft and translucent, about 2 minutes. Add celery and carrots and season with salt and pepper. Saute until all the vegetables are soft, about 5 minutes. Add tomatoes, basil, and bay leaves and simmer covered on low heat for 1 hour or until thick. Remove bay leaves and check for seasoning. If sauce still tastes acidic, add unsalted butter, 1 tablespoon at a time to round out the flavors.
Add half the tomato sauce into the bowl of a food processor. Process until smooth. Continue with remaining tomato sauce.
If not using all the sauce, allow it to cool completely and pour 1 to 2 cup portions into freezer plastic bags. This will freeze up to 6 months.