Cut the carrots into fine julienne and sprinkle with half of the juice of one lemon. Clean the melon, cut the flesh into balls with a baller.
Gently mix the melon balls with the cheese, carrots and cheese.
Mix the remaining juice of one lemon, mustard, oil, sugar, salt and pepper to make a spicy sauce and fold it into the lettuce.
Arrange on plates and bring to the table with baguette and butter.