To prepare the dressing: In a small bowl, combine the vinegar mustard, cumin, and sugar; season with salt and pepper. Whisk to blend. While whisking, slowly drizzle in the olive oil, mixing until the vinaigrette is emulsified. Set aside.
To prepare the salad: Fill a medium bowl with 2 cups of ice cubes and cover with cold water. Bring a pot of salted water to a boil over medium-high heat. Add the asparagus and blanch until tender but not mushy, about 3 minutes. Drain the asparagus in a colander and transfer to the ice water bath to stop the cooking. Drain again and place on a paper towel-lined plate to dry. Cut the asparagus stalks into thirds.
In a large mixing bowl, combine the blanched asparagus, parsley, artichokes, tomatoes, and watercress. Whisk the vinaigrette to combine and pour over the salad. Toss to coat and serve.