Heat the oil in a large frying pan and fry the onion for 4-5 minutes, add the tomatoes, Walnuts and beans and cook for 2-3 minutes. Stir in the vinegar and most of the basil, season to taste.
Spoon over the toast and scatter with the remaining basil and some chopped Walnuts.
Cooks tip: Try adding some pan fried diced pancetta to the tomato mix for extra flavour, or swap the cannellini beans for chick peas.
