Grilled Veggie Salad with Avocado Ranch

Name: Grilled Veggie Salad with Avocado Ranch
Ingredients: 1/2 large avocado; 1/4 cup buttermilk; 1/4 cup mayonnaise; Juice of 1 lemon (about 1/4 cup juice); 1/4 cup roughly chopped fresh chives, plus more for garnish; 1/4 cup chopped fresh dill, plus more for garnish; 1/4 cup fresh parsley leaves, plus more for garnish; 4 ears corn; 1 orange (or red or yellow) bell pepper, cut into planks; 8 ounces fresh green beans, ends trimmed and snapped in half; 5 teaspoons olive oil; Kosher saltand freshly ground black pepper; 2 romaine hearts, roughly chopped; 8 cherry tomatoes, quartered; 1/4 small red onion, thinly sliced