For the dressing, crumble half the Roquefort cheese, the mayonnaise, heavy cream, vinegar, salt and pepper in the bowl of a food processor fitted with a steel blade and process until combined but still chunky.
Arrange the lettuce leaves on a platter and place the tomatoes on top. Pour the dressing over the tomatoes. Crumble the remaining Roquefort and sprinkle it over lettuce and tomatoes.
2009, Ina Garten, All Rights Reserved