Blanch beans in lightly salted boiling water about 2 minutes. Drain and leave to cool. Cut into pieces.
Halve capsicum and cut into strips. Peel potatoes and slice. Tear lettuce leaves into strips. Mix beans, capsicum, potatoes, lettuce and tomato in a large bowl.
To make vinaigrette, whisk oil, vinegar and garlic until combined; add salt and pepper to taste. Pour over salad.
Break tuna into pieces with a fork. Place tuna, onion, eggs and olives on salad.
a bite of history
Salad niçoise, from Nice, France, is one of many classics open to interpretation, with olives, potatoes, green beans and a vinaigrette dressing regarded as essential. Some say that the salad should be served on a bed of lettuce; others favour tomatoes as the base. Some simply toss all the ingredients together.