Step 1

Place green bell pepper, carrot, and garlic cloves into a food processor and pulse a few times until the vegetables are very finely chopped.

Step 2

Transfer chopped vegetables into a large saucepan. Stir in tomato puree, crushed tomatoes, Italian seasoning, basil, and red pepper flakes; bring to a boil. Reduce heat to low and simmer uncovered until sauce has thickened, about 30 minutes. Stir in olive oil and simmer 1 to 2 more minutes. Sauce may be refrigerated up to 1 week.