Rub the inside of a bowl with the garlic and discard the debris. Add the vinaigrette ingredients and whisk together, adding enough vinegar to make it taste slightly sharp.
Cut the tomatoes into 4 or 6 wedges, depending on size. Cut the pepper in half lengthwise and remove the seeds and white pitch before cutting into 5mm strips.
Separate the lettuce leaves and assemble all the ingredients in a wide salad bowl, adding the drained and flaked tuna, if using. Season to taste.
Present the bowl of salad and moisten with the vinaigrette at the table. Before serving, toss thoroughly so that the eggs break up – the flavours will only come together if everything is tossed well.