In a large pot over medium heat, cook the onion in the olive oil until the onion is softened, about 6-9 minutes. Add the garlic and cook for another minute. Add the red pepper flakes and red wine and cook for about 3-5 minutes or until most of the wine has been absorbed. Add the remaining sauce ingredients and simmer over low heat for about 15-20 minutes, stirring occasionally. Add more salt to taste. Remove from the heat and let cool while preparing the rest of the lasagna.
1 tablespoon olive oil, 1 1/2 cups (200 grams) onion, 1 1/2 tablespoons (15 grams) garlic, 1/8 teaspoon red pepper flakes, 2/3 cup (158 ml) red wine, 28 ounces (794 grams) canned diced tomatoes, 14.5 ounces (411 grams) canned diced tomatoes, 6 ounces (170 grams) tomato paste, 1 1/2 teaspoons dried parsley, 2 tablespoons (7 grams) fresh basil, 1 1/4 teaspoons salt