In a large dutch oven, add olive oil and heat over medium heat. Add onion, celery and carrot and cook until the onion is translucent and the vegetables have begun to soften, 7 to 9 minutes.

Add Italian seasoning, garlic, salt, pepper and red pepper flakes to taste. Cook until the garlic is fragrant, 1 to 2 minutes.

Add ground beef and cook, stirring occasionally to break up any large chunks of meat and until the meat has been cooked through and no pink remains, 3 to 5 minutes.

Add tomato paste and cook for 2 to 3 minutes, then deglaze the pan with vegetable broth, stirring to scrape up any brown bits that have formed on the bottom of the pan. Cook until the broth is reduced, about 2 minutes.

Add the sun-dried tomatoes and whole peeled tomatoes and stir well to combine. Bring the sauce to a boil, then reduce heat to a simmer and cook for 35-45 minutes. Taste and adjust seasoning with salt and pepper as needed.