1. If you are using canned beans, drain them in a colander, wash them in cold water, then drain them again and spread on paper towels to dry before transferring them to a serving bowl.
2. If you are using dry beans, combine them with water in a 3- to 4-quart saucepan and bring to a boil.
3. Boil briskly for 2 minutes, remove from the heat and let the beans soak for 1 hour. Then cook them in the soaking water over low heat for 1 to 1½ hours, or until they are tender. Drain, transfer them to a serving bowl and cool.
4. To make the salad, combine the olive oil, lemon juice, salt and pepper and pour them over the beans. Add the scallions and parsley and gently mix them all together.
5. Transfer the beans to a platter, break the tuna into chunks and arrange them on top. This salad may be served alone as a first course.
