Put the lentils and bay leaf into a small saucepan with cold water to cover. Bring to a boil, reduce the heat, and cook at a low boil for about 20 minutes, until just chewy-tender. Drain, rinse briefly, and transfer to a bowl. Add the remaining ingredients, except the tomatoes, tossing well to coat with the oil and vinegar. Season with salt and pepper to taste.
Cover and refrigerate until about 10 minutes before serving. Just before serving, toss the tomatoes with the salad. Add a bit more oil and vinegar, if necessary, and pass cruets of both at the table.