Lidia Bastianich uses contrasting flavors and textures to make this upscale Italian starter.
For the verdure cotta (cooked vegetables): Preheat the oven to 375 degrees. Peel and trim the onions and slice into rounds about ¾ inch thick. Brush with some of the olive oil, and sprinkle salt lightly on both sides. Lay the onions on a baking sheet, and roast for 20 minutes or longer, until slightly softened and nicely caramelized. Cool, then separate the rounds into rings.
Meanwhile, drop the potatoes-whole, with skin on, into a pot with plenty of water. Bring to a gentle boil, and cook just until a sharp knife blade slides through the potatoes. Remove with a spider, and cut the potatoes into wedges about 1 ½ inches thick.
When the potatoes are out of the boiling water, drop the green beans in and cook until al dente, 4 minutes or so. Drain, and drop the beans into ice water to set the color. One they're chilled, drain and dry the beans, and cut into 2 inch lengths.
Combine the cooked vegetables in a large serving bowl with the olives, capers, and tomatoes. Sprinkle with the remaining salt and some freshly ground pepper, drizzle the rest of the olive oil and the red wine vinegar over vegetables, and tumble them to coat with dressing. Scatter the lettuce on top, then toss to distribute evenly. Serve immediately.