Wedge Salad with Tahini Green Goddess Dressing

Ingredients

1/2 cup mayonnaise
1/2 cup sour cream
1/2 cup tahini
1/4 cup fresh lemon juice
6 anchovy fillets (from 1 [2-ounce] can)
1 cup loosely packed fresh basil leaves
1 cup loosely packed fresh flat-leaf parsley leaves
1 cup loosely packed fresh cilantro leaves and tender stems, plus more for garnish
4 scallions, chopped (about 1/2 cup)
1/4 cup chopped fresh dill, plus more for garnish
1 1/4 teaspoons kosher salt, plus more to taste
1/4 teaspoon black pepperr, plus more to taste
2 small (1-pound) iceberg lettuce heads, outer leaves removed, each head cut through core into 6 wedges
2 Persian cucumbers, thinly sliced (about 1 1/2 cups)
6 medium radishes, thinly sliced (about 1 cup)
Toasted sesame seeds, for garnish