Sofrito

Heat the oil in a heavy-based metal frying pan or flameproof earthenware casserole. When it is very hot but not boiling, add the onion. As it cooks it will change texture and colour, turning from transparent to pink then orangey-brown. At this point, not before, add the tomato with or without the seeds, as you prefer. When the tomato is half-cooked, you can add one or two spoonfuls of water to help it caramelise. When the sauce is ready it will have the consistency of jam, and the secret is to make it in a kitchen ruled by patience and calm!