Finely chop the onion, celery, garlic, bell pepper and carrot.
Heat the oil in a large saucepan and gently sauté the chopped vegetables, under a lid, for about 8 minutes.
Meanwhile, chop the aubergine and courgette
Add the capers, chilli flakes, dried herbs, aubergine and courgette to the pan. Put the lid on and sauté for another 5 minutes or so.
Chop the tomatoes and add to the pan. Add the bay leaf and salt & pepper. Bring to the boil, then turn down the heat and gently simmer for about 25-35 minutes, until the vegetables are soft. You might need to add some water if it’s getting too sticky.
Remove the bay leaf and, using a stick blender or liquidizer, purée it until you get a textured or smooth sauce, depending on your liking.
Let it cool in the pan, then transfer it into plastic containers or freezer bags, and chill or freeze the portions for future meals.