"1 (10 to 12-inch) square salt block, at least 1 ½ inches thick 1 large shallot, finely chopped ¼ cup red wine vinegar 2 teaspoons Dijon mustard large garlic clove, minced ½ teaspoon anchovy paste ¾ cup extra-virgin olive oil, divided 1 teaspoon fresh thyme leaves 1 teaspoon chopped fresh tarragon leaves 1 teaspoon dried lavender 1 teaspoon coarsely ground black pepper, divided 2 (6-ounce) tuna steaks, about 1½ inches thick 4 red-skin or golden potatoes, thinly sliced 8 ounces haricot vert green beans or other young tender green beans, stems trimmed 1 head Boston lettuce, broken into leaves ¼ cup drained bottled capers ½ pint grape tomatoes, quartered lengthwise 3 hard-cooked eggs, peeled and quartered ½/ cup Niçoise or other oil-cured black olives 8 fresh basil leaves, cut into fine strips"