1/2 cucumber, thinly sliced (peel a seeded cucumber, rinse a seedless cucumber with peel left on)
1 ripe tomato, quartered and thinly sliced
1 small red onion or 1/2 medium red onion, thinly sliced
1 large or 2 medium romaine hearts, washed and chopped
3 to 4 tablespoons chopped fresh tarragon leaves or 2 teaspoons dried
2 tablespoons white balsamic vinegar or white wine
1/4 cup extra-virgin olive oil
Salt and freshly ground black pepper
Sesame seeds, for garnish