To prepare lemon, cut in half and scoop the seeds out with a spoon. Cut the flesh into cubes and set aside. Remove the marinated artichoke hearts from jar and drain. Remove sausage from package and slice. Heat olive oil in a pan and add sausage. Fry until sausage is ready and allow to cool a few minutes. In a bowl, combine artichokes with melon, and sausage. Sprinkle with a generous amount of tarragon. For dressing place all ingredients in a small bowl and whisk together. Pour dressing over the prepared salad and toss well. Garnish with more tarragon and enjoy.