This is closer to a vinaigrette than a sauce. It is not cooked. Peel and deseed the tomatoes. Chop the chives and coriander (which is an improvement on basil). Put in a bowl with the tomatoes and cover with olive oil. Add a small amount of lemon juice or Pedro Ximenez vinegar. Leave in the fridge for 2 or 3 days so that the oil begins to get infused with the flavour of the herbs.