Thinly slice the onion, celery, red pepper and garlic. Peel and chop the carrot and squash.
Heat the oil in a saucepan and gently sauté the onion, garlic and celery.
When they are soft, add the other chopped veggies, chilli flakes and rosemary. Stir for a minute, then add the tomatoes and vegetable stock.
Bring to the boil. Cook for about 15 minutes or until the vegetables are tender and the sauce is thick.
Using a handheld blender whiz the stew until you a get a thick sauce. Set aside. ( You can let it cool and refrigerate for up to 3 days.)
Cook the pasta following the instructions on the packet. Add the spinach to the pasta for the last minute of the cooking.
Drain the pasta and spinach then put it back in the pan. Add spoonfuls of the reheated sauce then mix well.
Use any remaining sauce for other dishes (such as soups, stews etc)
Serve warm.