For the sauce: pour off all but 1 tablespoon of the oil from the pot and return to medium heat until shimmering. Add the onion and 1/2 teaspoons salt and cook, stirring occasionally, until softened 5 to 7 minutes. Stir in the tomato paste, sugar, garlic, oregano, red pepper flakes, and 1/4 teaspoon pepper and cook until the tomato paste begins to Brown, 2 to 4 minutes. Add the water, tomatoes, and tomato sauce. Bring to a simmer, cover and cook, stirring occasionally, for one hour.