Mixed Salad with Tarragon

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