-- Spread some olive oil in the bottom of one or two very large roasting pans.
-- Take these out to a pleasant shady table along with your basket of tomatoes and the onions. (Perhaps 1/3 as many onions as tomatoes, but this is up to you.)
Cut the tomatoes roughly and put them in the pans, then add the roughly chopped onions.
Add peeled cloves of at least one complete head of garlic for each pan (more is good; for me I would use two for each pan).
Snip in plenty of rosemary. Toss all this with pepper, sea salt, and a good quantity of more olive oil.
Also a cup, perhaps, of good balsamic vinegar.
(You will see I use both yellow and red tomatoes here.)
When your oven has become very hot (about 450 Fahrenheit) put in your pans. Let the mixture roast for at least an hour, stirring occasionally so that the top layer becomes a bit “charred” and then is stirred under.
Of course you must watch this and if the oven is too hot, turn it lower but not too much.
You will want to cook this until it is nicely “cooked down” and not too juicy and the onions a bit caramalized, so, for me, I would let it roast perhaps two hours in all.
When you take it from the oven add the juice of one lemon to each pan along with the lemon zest. (If your pans are small you can of course use less zest.) Let this cool.
Now I must warn you: That woman will tell you that in my kitchen we are not modern. Beh! We have many good “appliances” electric (though we do not always prefer to use). Also my husband Niccolo has put in a “generator” so that we can still use these appliances when the electricity fails (as here it often does).
So, now -- put this roasted sauce through an electric blender if you have one (or you can use a “food mill” if you do not.)
Add some good bunches of basil as you blend, which will just gently give its flavor when the sauce is re-heated (which you will want to do before you use or before you package up to freeze).
And of course, at this point test again for the flavour. Is it too thick? You will figure out what to do. Perhaps a little wine?
This will be a very good sauce for many dishes.
But if you are like my husband, Niccolo, you will prefer that to this is added a very ample quantity of nicely browned ground beef, then some sliced brown mushrooms, which you will let “cook down to give off their moisture” before you add anything else.
And the last touch: (very important!)
Now you must add some more lemon zest, perhaps the zest of one lemon more for each pan that you have roasted (but taste this carefully as you heat it and let it simmer) and let the sauce cook gently on your “back burner” until it is absolutely as you would prefer.
(I have a neighbor who instead of lemon adds the juice and zest of orange, and this is also very good.)