Bring a large pot of water to a boil, salt it generously and cook the pasta until al dente according to package instructions. Reserve about ½ cup of the cooking water before draining.

Meanwhile, heat the olive oil in a large, deep skillet or Dutch oven over medium heat. Add the red onion, carrots, celery, red bell pepper, zucchini and sweet potato. Cook for 10–12 minutes, stirring often, until all the vegetables are soft.

Add the garlic, Italian seasoning and red chili flakes and continue to cook for another minute.

Stir in the tomato paste and cook for 1 minute, then pour in the tomato sauce and water. Season with salt and pepper and bring to a gentle simmer. Simmer for 5-10 minutes until the sauce thickens a bit.

Transfer everything to a blender (or use a stick blender) and blend until smooth. If needed, add a splash of reserved pasta water to loosen the sauce to your liking.

Return the sauce to the pan and add the cooked pasta. Add some more pasta water as needed. Stir in the Parmesan cheese and most of the parsley.

Serve hot, finished with the remaining parsley and extra Parmesan on top if you like.