That's all it is. I believe it was mentioned in another post. Couldn't be more simple.
A can of good tuna in olive oil, double the amount of cannellini - and here I prefer to cook my own because you are never sure of the consistency of canned. Thinly sliced red onion [ I prefer to deflame the onion slices in cold water for a few minutes at this time of year ]. Minced parsley, salt and pepper to taste. Depending on how I feel, some wine vinegar or not.
Great alone or as part of a salad composee with other vegetables.