In a large pot on medium heat, heat the oil. Add in the onions and garlic, sprinkle with salt and cook for 4 minutes until the garlic becomes fragrant. Add in the diced celery and carrot and cook for another 5 minutes.
Add in the chopped tomatoes, basil, oregano, chilli flakes and red wine vinegar and leave everything to cook for 25 minutes.
Once the tomatoes are completely stewed and the sauce has thickened you can serve it as it or use an immersion blender (or transfer to a blender) and blend until completely smooth.