Meanwhile, while the pasta is cooking, heat the oil in a separate large saucepan over medium-high heat. Add onion and cook for 5 minutes or until translucent. Add garlic and cook for an additional minute. Then stir in tomatoes, cinnamon, oregano, sugar, and red pepper flakes. Heat until the sauce just begins to boil, then reduce heat to medium-low, cover, and simmer for 10 minutes. Season with additional salt and pepper if needed.