Thinly slice the garlic. Cut the tomatoes with the seeds into chunks.
Fry garlic in olive oil for a few until cooked but not yet coloured.Add the chilli flakes followed by puréed tomato and salt. Bring to a fairly brisk boil and cook until the sauce has a little body (the bubbles get a bit bigger) but not thick. The tomatoes should taste fresh, but no longer raw. Season with pepper and add the remaining oil to finish.