Salad Nicoise

Salad:
4 red skinned potatoes, quartered
3 hard-boiled eggs, quartered
1 cup cooked green beans, trimmed
3 plum tomatoes, chopped
1 head romainne lettuce, chopped
1/2 cup canned sliced green olives
1/4 cup red onion, diced
1 can tuna

Dressing:
1/3 cup balsamic vinegar
1/4 cup olive oil
1 tbsp. dijon mustard
1/2 tsp lemon juice
1 tsp sugar

Layer salad in a large bowl or platter. Pour dressing before serving.