Add the canned tomatoes (with juices) to a large bowl and use your hands to break the whole tomatoes up.
Add the olive oil, butter, and onions to a soup pot or Dutch oven and sauté over medium heat for 5-7 minutes or until softened.
Stir in the garlic and cook for 30 seconds.
Add in the tomatoes, Italian seasoning, oregano, sugar, salt, and red pepper flakes. Give it a good stir. Once the sauce starts to bubble, cover the pot with the lid slightly open and reduce the heat and simmer for 30 minutes (adjust between medium-low and low heat as needed to maintain a constant simmer).
Stir in the fresh basil and give the sauce a taste and season with extra salt & some pepper as needed.
