I first started experimenting with my own tomatoe sauce about a year ago. I chucked a can of diced tomatoes into a pot and stirred. Then I added some spices and stirred. This recipe follows on from that first experiment. Now I use fresh tomatoes and herbs, and stir.
I used 4kg of fresh tomatoes, 2 400g cans of skinned, diced Italian tomatoes, about 20 small onions (the ones you'd use to make pickled onions), garlic, celery, salt and pepper.
Peel the purple onions (this is the first time I have used purple onions in my sauce, normally I use white onions), then slice and dice them. While doing this, pour quite a large glug of good quality olive oil into your pot and heat up on the stove. Once the oil is hot enough, add the small onions and coat with the oil. Then add the purple onions and diced celery. Sweat them down until the small onions start caramelising. Add 2 tablespoons of chopped garlic, stir and cook for a further 10 minutes or so on a low heat, making sure that the garlic does not burn or go brown.
Peel the tomatoes, making sure to cut out the hard core. Add the fresh tomatoes to the onions and garlic. Open the two cans of Italian tomatoes and add to the pot as well.
Then cook until the tomatoes start breaking apart easily with a spoon. At this point I turn up the heat to boil off at least half of the liquid. Then I blitz the sauce down in a food processor and return to the pot to cook off any liquid that still remains.