Heat the olive oil in a large heavy pot with a tight-fitting lid over medium heat. When the oil is hot, add the garlic and stir until fragrant and light golden, 2-3 minutes. Add the red pepper flakes and oregano and stir for another minute.
Add the carrot, onion, and basil sprig. Pour the canned tomatoes, including all the juices on top, covering the other ingredients. Stir in the tomato paste. When the tomato juice begins to boil, reduce to low heat and cover.
Simmer at least 30 minutes, up to an hour, depending how much you’d like to develop the flavor of the sauce. Remove the basil, carrots, and onions, which you can either discard or eat separately.
Scoop a few tablespoons of the liquid part of the sauce into a small bowl. Mix the miso together with the sauce and dissolve it completely using a fork. Pour the mixture into the pot of sauce.
Use a wooden spoon, muddle, or other device to crush and chop the tomatoes to your desired consistency. Taste the sauce and stir in salt as needed.
Garnish with fresh parsley and basil and serve over boiled pasta, as a dipping sauce, or any other way you prefer.