How to Make It
In a large saucepan of boiling, salted water, cook the snap peas until just barely tender, 1 to 2 minutes. Drain, rinse with cold water and drain thoroughly. Pat dry with paper towels.
Arrange the salmon on individual plates, overlapping the slices as necessary. In a large bowl, whisk the lemon juice, salt and pepper. Add the oil slowly, whisking. Add the snap peas, watercress and scallions and toss. Mound the salad in the center of each plate and serve.