Heat 2 tablespoons vegetable oil in a heavy skillet over medium heat. Add cayenne and sugar and stir until sugar dissolves. Add walnuts and stir until coated. Continue stirring until walnuts are toasted. Using a slotted spoon, transfer walnuts to foil-lined sheet and cool.
Whisk walnut oil, vinegar and 3 tablespoons chopped fresh cilantro in a medium bowl until well blended. Season to taste with salt and pepper.
Prepare barbecue (medium high heat). Combine 2 tablespoons vegetable oil, onion wedges and pepper strips in large bowl. Season to taste with salt and pepper. Grill vegetables until tender and blackened in spots. Transfer to large bowl. Add watercress. Toss with dressing. Arrange on platter. Garnish with candied walnuts.
c.1997, M.S. Milliken & S. Feniger, all rights reserved