Heat the olive oil in a small Dutch oven over medium heat. Add the onion, oregano, and crushed red pepper flakes. Cook, stirring often, for 5 minutes, or until the onion is soft. Add the minced garlic and cook, stirring constantly, for 1 minute. Add the tomato sauce. Using an immersion blender (or blender), blend the canned whole tomatoes. Pour them into the Dutch oven and stir until well combined. Cover with a lid and let simmer for 30 minutes or up to 2 hours. Taste and season with sea salt, freshly cracked pepper, and a touch of sugar (if desired). Add the chopped basil and ladle over prepared pasta. Enjoy.