To prepare the romesco sauce: Put the tomato and garlic into a small baking pan and roast in a preheated 400-degree oven 20-25 minutes, until tender and starting to brown.
Heat 1 tablespoon olive oil in a small skillet set on medium heat. Add the bread crumbs and almonds, cooking until golden.
Puree the roasted tomato and garlic in a food processor. Add the bread crumb mixture, processing until the almonds are very finely chopped. Add the crushed pepper, cayenne, salt, 4 tablespoons vinegar and the remaining 3 tablespoons olive oil. Process until thickened.
To prepare the salad: Cut the potato in half, place in a saucepan, cover with water and cook until tender, about 20-25 minutes. Drain; peel and cut into thin slices.
Cover the onion with cold water and set aside 10 minutes. Drain and pat dry. Bring a pan of water to the boil, add the beans and cook 5 minutes, until tender. Remove the beans with a slotted spoon to a bowl of ice water. Bring the water back to a boil, add the zucchini and time 1 minute. Add to the beans in the ice water. When chilled, drain and pat dry.
Combine the potatoes, onions, beans, zucchini, cucumber, olives, pimento, egg, several grindings of pepper and parsley with the dressing. Let sit 1 hour at room temperature or refrigerate for longer storage. Stir in the remaining tablespoon vinegar if needed.