Place a large sauce pot over medium-low heat. Add the butter. Once melted add the onions and garlic. Then sauté for 12-14 minutes, stirring occasionally, until the onions are very soft, but not dark.
Add the shredded carrots and dried thyme, then sauté another 5 minutes to soften.
Finally add the crushed tomatoes and juices, tomato sauce, 1 1/2 teaspoons sea salt, and 1 teaspoon ground black pepper. Raise the heat to medium and bring to a simmer. Then cover the pot, leaving a crack for venting, and simmer for 30 minutes. Lift the lid and stir occasionally.
Stir in the chopped basil and simmer another 2-3 minutes. Taste and season accordingly.