Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   3      cups          water
   2      cans          cannellini beans
     1/3  cup           olive oil
   3      teaspoons     red wine vinegar
   1      teaspoon      salt
                        fresh pepper to taste
   1      medium        red onion
  12      ounces        tuna -- drained

Preparation:

Mix together oil, vivegar, salt and pepper. Pour over beans and onion in a shallow bowl. Cover and refrigerate at least 1 hour. Transfer bean mixture to serving platter with slotted spoon. Break tuna into chunks and arrange on bean mixture.