Garden Salad with Herbs and Sour-Cherry Dressing

2 teaspoons sherry vinegar or aged red-wine vinegar

1 teaspoon fresh lemon juice

Kosher salt and freshly ground pepper

2 tablespoons extra-virgin olive oil

6 ounces fresh sour cherries, rinsed, drained, pitted, and halved or quartered (1 cup)

1 fennel bulb, halved length-wise, cored, and thinly sliced, plus ½ cup fronds

2 cups mixed fresh tender-herb leaves, such as shiso, basil, tarragon, anise hyssop, and mint

5 cups mixed greens, such as watercress, amaranth, tatsoi, and arugula

2 spring onions, thinly sliced (½ cup)

6 radishes, thinly sliced (1 cup)